[AArch64] Add support for NEON scalar signed saturating absolute value and
scalar signed saturating negate instructions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192734 91177308-0d34-0410-b5e6-96231b3b80d8
Reflow slightly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192736 91177308-0d34-0410-b5e6-96231b3b80d8
Remove this regression test now that PR17578 is fixed (r192674). The fix is to
reject this test case at the Sema stage, so no CodeGen test should be needed.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192738 91177308-0d34-0410-b5e6-96231b3b80d8