[middle-end,patch] Making __builtin_signbit type-generic

[Paolo Carlini]

... I'm committing the below. Tested x86_64-linux.

Thanks,
Paolo.

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2015-08-19  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/c_global/cmath: Revert fix for libstdc++/58625, no
	longer necessary (__builtin_signbit is now type-generic).
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Index: include/c_global/cmath
===================================================================
--- include/c_global/cmath	(revision 227003)
+++ include/c_global/cmath	(working copy)
@@ -650,10 +650,10 @@
     isnormal(_Tp __x)
     { return __x != 0 ? true : false; }
 
-  // The front-end doesn't provide a type generic builtin (libstdc++/58625).
+  // Note: c++/36757 is fixed, __builtin_signbit is type-generic.
   constexpr bool
   signbit(float __x)
-  { return __builtin_signbitf(__x); }
+  { return __builtin_signbit(__x); }
 
   constexpr bool
   signbit(double __x)
@@ -661,7 +661,7 @@
 
   constexpr bool
   signbit(long double __x)
-  { return __builtin_signbitl(__x); }
+  { return __builtin_signbit(__x); }
 
   template<typename _Tp>
     constexpr typename __gnu_cxx::__enable_if<__is_integer<_Tp>::__value,