* lib/sys_types.in.h (blksize_t, blkcnt_t): New definitions.
* m4/sys_types_h.m4 (gl_SYS_TYPES_H): Set HAVE_BLKSIZE_T and
HAVE_BLKCNT_T.
* modules/sys_types-h (Makefile.am): Substitute HAVE_BLKSIZE_T and
HAVE_BLKCNT_T.
* tests/test-sys_types-h.c: Check that blksize_t and blkcnt_t are
defined. Include intprops.h. Check the signedness of various types.
* modules/sys_types-h-tests (Depends-on): Add assert-h, intprops.
* doc/posix-headers/sys_types.texi: Mention the issues with blksize_t
and blkcnt_t.