Make compiling without gzip file operation support the default
(define WITH_GZFILEOP or use --zlib-compat to enable them).
Add initial support for compiling in a zlib-compatible mode, this currently only
enables gzip file operations and sets the ZLIB_COMPAT flag.
Conflicts:
test/minigzip.c
This patch allows zlib to compile cleanly with the -Wcast-qual gcc
warning enabled, but only if ZLIB_CONST is defined, which adds
const to next_in and msg in z_stream and in the in_func prototype.
A --const option is added to ./configure which adds -DZLIB_CONST
to the compile flags, and adds -Wcast-qual to the compile flags
when ZLIBGCCWARN is set in the environment.