[X86] Immediate forms of far call/jump are not valid in x86-64.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224678 91177308-0d34-0410-b5e6-96231b3b80d8
strnlen isn't available on some platforms, use StringRef instead

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224679 91177308-0d34-0410-b5e6-96231b3b80d8