Increase the minimum CMake version to 3.4.

CMake 3.2 added FindIntl.cmake for gettext.
CMake 3.4 added STRING(APPEND), which is used by Qt5's CMake files.

Update the toplevel project's CMake requirement and remove the
requirements on all lower-level projects, except for third-party
libraries.

Reported by @DankRank.

CMakeLists.txt

@@ -1,5 +1,5 @@
 # ROM Properties Page Shell Extension
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
+CMAKE_MINIMUM_REQUIRED(VERSION 3.4)
 CMAKE_POLICY(SET CMP0048 NEW)
 
 # Read the project version.

src/CMakeLists.txt

@@ -1,4 +1,3 @@
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 PROJECT(src)
 
 # Check for Large File Support.

src/amiibo-data/CMakeLists.txt

@@ -1,5 +1,4 @@
 # amiibo database data and compiler.
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/gtk/CMakeLists.txt

@@ -1,5 +1,4 @@
 # GTK+ UI frontends
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/gtk/gtk3/CMakeLists.txt

@@ -3,7 +3,6 @@
 # - Caja 1.18 (MATE)
 # - Nemo (Cinnamon)
 # - Thunar 1.8 (XFCE)
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/gtk/gtk4/CMakeLists.txt

@@ -1,6 +1,5 @@
 # GTK+ 4.x UI frontend
 # TODO: Not supported by any file browsers yet...
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/gtk/thumbnailer-dbus/CMakeLists.txt

@@ -1,5 +1,4 @@
 # D-Bus Thumbnailer for rom-properties
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/gtk/xfce/CMakeLists.txt

@@ -1,6 +1,5 @@
 # GTK+ 2.x UI frontend for:
 # - Thunar 1.6 (XFCE)
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/kde/CMakeLists.txt

@@ -1,5 +1,4 @@
 # KDE (Qt) UI frontends
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/kde/kde4/CMakeLists.txt

@@ -1,5 +1,4 @@
 # KDE 4.x UI frontend
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/kde/kf5/CMakeLists.txt

@@ -1,5 +1,4 @@
 # KDE Frameworks 5.x UI frontend
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/kde/kf6/CMakeLists.txt

@@ -1,5 +1,4 @@
 # KDE Frameworks 6.x UI frontend
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libcachecommon/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Common cache management functions used by both Cache Manager and rp-download.
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libcachecommon/tests/CMakeLists.txt

@@ -1,5 +1,4 @@
 # libcachecommon test suite
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libi18n/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Internationalization support code.
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libromdata/CMakeLists.txt

@@ -1,5 +1,4 @@
 # RomData subclasses and factory class.
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libromdata/tests/CMakeLists.txt

@@ -1,5 +1,4 @@
 # libromdata test suite
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpbase/CMakeLists.txt

@@ -1,5 +1,4 @@
 # rom-properties base library
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpbase/tests/CMakeLists.txt

@@ -1,5 +1,4 @@
 # librpbase test suite
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpcpu/CMakeLists.txt

@@ -1,5 +1,4 @@
 # rom-properties CPU support library
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpcpu/tests/CMakeLists.txt

@@ -1,5 +1,4 @@
 # librpcpu test suite
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpfile/CMakeLists.txt

@@ -1,5 +1,4 @@
 # rom-properties file handling library
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpsecure/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Security functionality
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librptexture/CMakeLists.txt

@@ -1,5 +1,4 @@
 # rom-properties texture decoding library
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librptexture/tests/CMakeLists.txt

@@ -1,5 +1,4 @@
 # librptexture test suite
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/librpthreads/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Threading wrapper library
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libunixcommon/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Unix and Unix-like systems common code
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libwin32common/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Windows common code
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/libwin32ui/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Windows UI common code
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/res/CMakeLists.txt

@@ -1,3 +1,4 @@
+# Resources
 PROJECT(res)
 
 IF(BUILD_GTK2 OR BUILD_GTK3)

src/rp-download/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Online downloader program for external images
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/rp-stub/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Stub executable for Unix and Unix-like thumbnailers
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/rpcli/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Command line interface
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/svrplus/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Windows DLL registration frontend
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all

src/win32/CMakeLists.txt

@@ -1,5 +1,4 @@
 # Windows UI frontend
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 CMAKE_POLICY(SET CMP0048 NEW)
 IF(POLICY CMP0063)
 	# CMake 3.3: Enable symbol visibility presets for all