Fix isblank / isascii / toascii namespace (bug 17635).

Fix isblank / isascii / toascii namespace (bug 17635).

Use of isblank brings in isascii and toascii, but isblank is a C99
function and the other two aren't; similarly, isascii and toascii are
UNIX98 functions and bring in isblank, which isn't.  (Not a
conformance issue because of the is* and to* reservation, but still
contrary to glibc practice.)  This patch fixes this by splitting
isblank out of ctype-extn.c to a separate ctype-c99.c.  isblank_l is
also moved to a separate file, ctype-c99_l.c (non-XSI POSIX.1-2008 has
isblank_l, but isascii / toascii are marked OB XSI).  (In principle
all these functions could go in separate files - that's optimal for
static linking - but they are also all very small, and splitting them
all out is not needed to fix the present bug.)

Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by the patch - the ordering in which new and
existing sources are listed in ctype/Makefile is arranged so functions
go in the same order so that this comparison works).

	[BZ #17635]
	* ctype/ctype-c99.c: New file.  isblank implementation moved from
	...
	* ctype/ctype-extn.c: ... here.
	(__isblank_l): Move to ...
	* ctype/ctype-c99_l.c: ... here.  New file.
	* ctype/Makefile (routines): Add ctype-c99 and ctype-c99_l.
	* conform/Makefile (test-xfail-ISO99/ctype.h/linknamespace):
	Remove variable.
	(test-xfail-ISO11/ctype.h/linknamespace): Likewise.
	(test-xfail-XPG3/ctype.h/linknamespace): Likewise.
	(test-xfail-XPG4/ctype.h/linknamespace): Likewise.
	(test-xfail-UNIX98/ctype.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/ctype.h/linknamespace): Likewise.