Build fix for gcc builtin
Build fix for gcc builtin

The __sync_add_and_fetch() builtin parameter is volatile but clang has
'different' type checking and ends up accepting this code.

Undo the C++ cast from r198505 to get libc++/LLVM building with g++ while this
is investigated.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@199494 91177308-0d34-0410-b5e6-96231b3b80d8

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