Bug#678033: hotfix

[Václav Šmilauer]

The fix Sami mentioned works only when _compiling_ glibc with clang, not 
when clang uses headers which were otherwise compiled for use with gcc. 
The attached patch is a trivial hotfix modifying an already installed 
file, for those who need the fix right now.
--- /usr/include/c++/4.7/type_traits.orig	2012-08-30 11:41:05.328540761 -0400
+++ /usr/include/c++/4.7/type_traits	2012-08-30 11:41:59.404541874 -0400
@@ -252,7 +252,7 @@
     struct __is_floating_point_helper<long double>
     : public true_type { };
 
-#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
+#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128) && !defined(__clang__)
   template<>
     struct __is_floating_point_helper<__float128>
     : public true_type { };