Merge LLVM/Clang 3.4 into PNaCl's branch This fixes up various merge conflicts. The PNaCl branch of Clang contained various changes cherry-picked from between 3.3 and 3.4, so these no longer appear as localmods after the merge. This includes changes to: * atomics * C++ method pointers for le32 * use of pow() intrinsic BUG=https://code.google.com/p/nativeclient/issues/detail?id=3757 TEST=PNaCl toolchain trybots Review URL: https://groups.google.com/forum/#!topic/native-client-reviews/OD-h-xSTCu4