* libc/ctype/ctype_c.c: Move inclusion of ctype_iso.h and

	* libc/ctype/ctype_c.c: Move inclusion of ctype_iso.h and
	ctype_cp.h out of ALLOW_NEGATIVE_CTYPE_INDEX case.
	(__ctype_ptr__): Constify in !_MB_CAPABLE case.  Otherwise,
	de-constify in !ALLOW_NEGATIVE_CTYPE_INDEX case, too.  Add comment.
	(__set_ctype): Set __ctype_ptr__ pointer according to definition
	of ALLOW_NEGATIVE_CTYPE_INDEX.
	* libc/include/ctype.h (__ctype_ptr__): Constify in !_MB_CAPABLE case.