[x86] Teach the new vector shuffle lowering about VBROADCAST and
VPBROADCAST.

This has the somewhat expected pervasive impact. I don't know why
I forgot about this. Everything seems good with lots of significant
improvements in the tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218724 91177308-0d34-0410-b5e6-96231b3b80d8
[AVX512] Remove space before \t in AsmStrings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218725 91177308-0d34-0410-b5e6-96231b3b80d8