ARM NEON: add _f16 support to a couple of vector-shuffling intrinsics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202137 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64 NEON: add 64-bit scalar intrinsics for _f64 mla/mls etc.

These seem to be supported by GCC, and do make sense architecturally so we
should probably have them.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202138 91177308-0d34-0410-b5e6-96231b3b80d8