* include/std/numbers [!__STRICT_ANSI__ && _GLIBCXX_USE_FLOAT128]
	(e_v, log2e_v, log10e_v, pi_v, inv_pi_v, inv_sqrtpi_v, ln2_v, ln10_v)
	(sqrt2_v, sqrt3_v, inv_sqrt3, egamma_v, phi_v): Add explicit
	specializations for __float128.
	* testsuite/26_numerics/numbers/float128.cc: New test.

From-SVN: r274145