MSVC 2013 doesn't like the updated Google Test:
extlib\googletest\googletest\include\gtest/internal/gtest-port.h(2102):
error C3409: empty attribute block is not allowed
Also, Qt 5.8 isn't present on AppVeyor anymore. Use Qt 5.13, which is
available for MSVC 2015.
In file included from C:/projects/rvthtool/extlib/googletest/googletest/include/gtest/internal/gtest-internal.h:40:0,
from C:/projects/rvthtool/extlib/googletest/googletest/include/gtest/gtest.h:58,
from C:\projects\rvthtool\extlib\googletest\googletest\src\gtest-all.cc:39:
C:/projects/rvthtool/extlib/googletest/googletest/include/gtest/internal/gtest-port.h:1782:3: error: 'AutoHandle' does not name a type
AutoHandle thread_;
^~~~~~~~~~