* pkg.[ch], main.c, check/check-missing: Don't recurse Requires at
all unless we need to. Add check. Again, thanks to Loïc Minier
for most of the idea and the implementation.
* pkg.[ch], parse.[ch], main.c, check/Makefile.am,
check/check-missing, check/missing-requires-private.pc:
Skip Requires.private unless we need to look at them for cflags.
Add test case. Thanks to Loïc Minier for most of the idea and the
implementation. Debian #475031