2011-05-09  Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/48933
	* include/c_global/cmath (acosh, asinh, atanh, cbrt, copysign,
	erf, erfc, exp2, expm1, fdim, fma, fmax, hypot, ilogb, lgamma,
	llrint, llround, log1p, log2, logb, lrint, lround, nearbyint,
	nextafter, nexttoward, remainder, remquo, rint, round, scalbln,
	scalbn, tgamma, trunc): Use __enable_if on the return type.
	* include/tr1/cmath: Likewise.
	* testsuite/26_numerics/headers/cmath/overloads_c++0x_neg.cc: New.
	* testsuite/tr1/8_c_compatibility/cmath/overloads_neg.cc: Likewise.

From-SVN: r173574