[patch] Minor simplification in <functional>

[Jonathan Wakely]

This avoids a template instantiation when storing a function pointer
in a std::function.

At some point I want to extend the definition of
__is_location_invariant to include trivially-copyable object types.
I suspect this may be why boost::function can perform significantly
better than our std::function in some cases.

Tested x86_64-linux, committed to trunk.

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commit 11ba841cb0b5655c974dfed32330b077a4d3b312
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Apr 16 18:21:28 2014 +0100

    	* include/std/functional (__is_location_invariant): Use __or_ helper.

diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional
index 0e80fa3..295022d 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -1747,8 +1747,7 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
    */
   template<typename _Tp>
     struct __is_location_invariant
-    : integral_constant<bool, (is_pointer<_Tp>::value
-			       || is_member_pointer<_Tp>::value)>
+    : __or_<is_pointer<_Tp>, is_member_pointer<_Tp>>::type
     { };
 
   class _Undefined_class;