[SystemZ] Add missing high-word facility instructions

There are a few instructions provided by the high-word facility (z196)
that we cannot easily exploit for code generation.  This patch at least
adds those missing instructions for the assembler and disassembler.

This means that now all nonprivileged instructions up to z13 are
supported by the LLVM assembler / disassembler.

llvm-svn: 306821