Support the built-in type-trait support in gcc 4.7 and later. Thanks to Albert Wong for the patch.
Support the built-in type-trait support in gcc 4.7 and later. Thanks to Albert Wong for the patch.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@212727 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx