towards pkg-config 0.30 - bugfixes and enhancments

[Alexey Tourbin]

Hello,

Would you please review my changes to pkg-config?  They fix quite a
few bugs rarely seen, because .pc files are usually simple enough.
One notable example is that "Requires: foo >=2 Requires: foo >= 1" are
now handled properly (in pkg-config 0.29.2, the dependency on "foo >=
2" was ignored).  I also suggest that in the "Requires: foo
Requires.private: foo >= 1" case, the version should rather be check
on behalf of Requires.  I also tackle the problem of wayland-*-devel
dependencies (in lieu of recent developments) and suggest a tentative
solution.

The changes are at https://github.com/svpv/pkg-config, and they are as follows:

[HEAD]
Use getc_unlocked instead of getc
check: Add test for enhanced versions
check: Add test for multiline fields
Revamped dependency loading in main.c, added --disable-recursion
Permit multiple Cflags lines
Revamped Libs and Libs.private parsing
Factored verify_info() to be called before load_requires()
Factored load_requires() to load Requires and Requires.private
Reimplemented --print-requires without pkg->required_versions
Permit multiple Requires/Requires.private/Conflicts lines
Simplify and improve parse_module_list
[pkg-config-0.29.2-1-g2dd2b19]