libstdc++: Stop using _GLIBCXX_USE_C99_MATH_TR1 in <cmath>

libstdc++: Stop using _GLIBCXX_USE_C99_MATH_TR1 in <cmath>

Similar to the three commits r14-908, r14-909 and r14-910, the
_GLIBCXX_USE_C99_MATH_TR1 macro is misleading when it is also used for
<cmath>, not only for <tr1/cmath> 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 <math.h> functions using
-std=c++11 for the checks. Use the new macro defined by those checks in
the C++11-specific parts of <cmath>, and in <complex>, <random> etc.

The check that defines _GLIBCXX_NO_C99_ROUNDING_FUNCS is only needed for
the C++11 <cmath> checks, so remove that from GLIBCXX_CHECK_C99_TR1 and
only do it for GLIBCXX_ENABLE_C99.

libstdc++-v3/ChangeLog:

	* acinclude.m4 (GLIBCXX_ENABLE_C99): Add checks for C99 math
	functions and define _GLIBCXX_USE_C99_MATH_FUNCS. Move checks
	for C99 rounding functions to here.
	(GLIBCXX_CHECK_C99_TR1): Remove checks for C99 rounding
	functions from here.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/bits/random.h: Use _GLIBCXX_USE_C99_MATH_FUNCS instead
	of _GLIBCXX_USE_C99_MATH_TR1.
	* include/bits/random.tcc: Likewise.
	* include/c_compatibility/math.h: Likewise.
	* include/c_global/cmath: Likewise.
	* include/ext/random: Likewise.
	* include/ext/random.tcc: Likewise.
	* include/std/complex: Likewise.
	* testsuite/20_util/from_chars/4.cc: Likewise.
	* testsuite/20_util/from_chars/8.cc: Likewise.
	* testsuite/26_numerics/complex/proj.cc: Likewise.
	* testsuite/26_numerics/headers/cmath/60401.cc: Likewise.
	* testsuite/26_numerics/headers/cmath/types_std_c++0x.cc:
	Likewise.
	* testsuite/lib/libstdc++.exp (check_v3_target_cstdint):
	Likewise.
	* testsuite/util/testsuite_random.h: Likewise.