Add crc32 instruction and intrinsics. Add a new class of prefix

Add crc32 instruction and intrinsics. Add a new class of prefix
bytes for F2 0F 38 and propagate. Add a FIXME for a set
of possibilities which correspond to intrinsics already used.

New test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78508 91177308-0d34-0410-b5e6-96231b3b80d8