conformtest: clean up POSIX expectations for sys/mman.h, sys/stat.h, sys/types.h.

Continuing the series of patches to clean up conformtest expectations
for "POSIX" (1995/6) based on review of the expectations against the
standard, this patch cleans up expectations for sys/mman.h, sys/stat.h
and sys/types.h.  Tested x86_64; no new XFAILs needed.

	* conform/data/sys/mman.h-data [POSIX] (size_t): Do not require
	type.
	[POSIX] (off_t): Likewise.
	* conform/data/sys/stat.h-data (S_IRGRP): Require constant.
	[POSIX] (S_ISBLK): Require macro.
	[POSIX] (S_ISCHR): Likewise.
	[POSIX] (S_ISDIR): Likewise.
	[POSIX] (S_ISFIFO): Likewise.
	[POSIX] (S_ISREG): Likewise.
	[POSIX || XPG3 || XPG4 || UNIX98] (S_TYPEISTMO): Do not list
	optional-macro.
	* conform/data/sys/types.h-data [POSIX] (blkcnt_t): Do not require
	type.
	[POSIX] (time_t): Likewise.
	[POSIX] (timer_t): Likewise.