Do not use -Wno-strict-prototypes.

Two glibc makefiles use -Wno-strict-prototypes.  I don't know if this
was needed before my recent conversion of many function definitions to
prototype style, but it's not needed now; this patch removes it.

Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by the patch).

	* posix/Makefile (CFLAGS-regex.c): Remove variable.
	* resolv/Makefile (+cflags): Do not use -Wno-strict-prototypes.