Add range checking for the immediate operand and handle the "mov" mnemonic
choosing between encodings based on the value of the immediate. Add tests
for fixups, encoding choice and values, and diagnostic for out of range values.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135500 91177308-0d34-0410-b5e6-96231b3b80d8