libstdc++: Stop using TR1 macros in <cctype> and <cfenv>

libstdc++: Stop using TR1 macros in <cctype> and <cfenv>

As with the two commits before this, the _GLIBCXX_USE_C99_CTYPE_TR1 and
_GLIBCXX_USE_C99_FENV_TR1 macros are misleading when they are also used
for <cctype> and <cfenv>, not only for TR1 headers. It is also wrong,
because the configure checks for TR1 use -std=c++98 and a target might
define the C99 features for C++11 but not for C++98.

Add separate configure checks for the <ctype.h> and <fenv.h> features using -std=c++11
for the checks. Use the new macros defined by those checks in the
C++11-specific parts of <cctype>, <cfenv>, and <fenv.h>.

libstdc++-v3/ChangeLog:

	* acinclude.m4 (GLIBCXX_USE_C99): Check for isblank in C++11
	mode and define _GLIBCXX_USE_C99_CTYPE. Check for <fenv.h>
	functions in C++11 mode and define _GLIBCXX_USE_C99_FENV.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/c_compatibility/fenv.h: Check _GLIBCXX_USE_C99_FENV
	instead of _GLIBCXX_USE_C99_FENV_TR1.
	* include/c_global/cfenv: Likewise.
	* include/c_global/cctype: Check _GLIBCXX_USE_C99_CTYPE instead
	of _GLIBCXX_USE_C99_CTYPE_TR1.