conformtest: Fix st_blksize, st_blocks expectations for XPG3, XPG4.

The conformtest expectations expect the struct stat fields st_blksize
and st_blocks to be of types blksize_t and blkcnt_t.  But XPG4 does
not have those types, using long instead, and XPG3 does not have these
fields at all.  This patch adjusts the expectations for those
standards, XFAILing them for XPG4 to allow for systems where the
typedefs don't correspond to long.

Tested for x86_64 and x86.

	* conform/data/sys/stat.h-data (st_blksize): Do not expect for
	[XPG3].  Expect type long and XFAIL for [XPG4].
	(st_blocks): Likewise.