[PATCH] Patched clang to emit x86 blends as shufflevectors.

[Rafael Ávila de Espíndola]

I just realized that one advantage of expanding the _builtins in clang is that it would allow us to remove the redundant ones from llvm in the future. Can you leave a FIXME about it in one of the tests?

http://reviews.llvm.org/D3601