[X86] Add __builtin_ia32_selectss_128 and __builtin_ia32_selectsd_128 that is...

[X86] Add __builtin_ia32_selectss_128 and __builtin_ia32_selectsd_128 that is suitable for use in scalar mask intrinsics.

This will convert the i8 mask argument to <8 x i1> and extract an i1 and then emit a select instruction. This replaces the '(__U & 1)" and ternary operator used in some of intrinsics. The old sequence was lowered to a scalar and and compare. The new sequence uses an i1 vector that will interoperate better with other mask intrinsics.

This removes the need to handle div_ss/sd specially in CGBuiltin.cpp. A follow up patch will add the GCCBuiltin name back in llvm and remove the custom handling.

I made some adjustments to legacy move_ss/sd intrinsics which we reused here to do a simpler extract and insert instead of 2 extracts and two inserts or a shuffle.

llvm-svn: 336622