[X86] Add intrinsics for KTEST instructions.

These intrinsics use the same implementation as PTEST intrinsics, but use vXi1 vectors.

New clang builtins will be accompanying them shortly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341259 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed