[X86] Remove masking from pternlog llvm intrinsics and use a select instruction instead.

Because the intrinsics in the headers are implemented as macros, we can't just use a select builtin and pternlog builtin. This would require one of the macro arguments to be used twice. Depending on what was passed to the macro we could expand an expression twice leading to weird behavior. We could maybe declare our local variable in the macro, but that would need to worry about name collisions.

To avoid that just generate IR directly in CGBuiltin.cpp.

Differential Revision: https://reviews.llvm.org/D47125

llvm-svn: 332891