[libcxx] r199494 - Build fix for gcc builtin

[Joerg Sonnenberger]

On Fri, Jan 17, 2014 at 02:24:23PM -0000, Alp Toker wrote:
> Author: alp
> Date: Fri Jan 17 08:24:23 2014
> New Revision: 199494
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=199494&view=rev
> Log:
> 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.

Please revert this. I gave you two options to deal with it -- the easy
workaround of adding the const cast and the harder option of merging the
implementation from libc++abi as Howard mentioned before. This change is
just hiding the issue again.

Joerg