Add inline code on 64-bit to BinaryOpICStubs for SMI to check for scenarios where a heap number may be representable by SMI.
Performance: Allow unaligned read on s390 and s390x to improve octane(run-regexp)benchmark by ~18%
perf enhancement: improve CopyCharsUnsigned non-conversion cases and undo unaligned read access as it gives no additional perf improvement
Fix LB encoding, disassembler and simulator issues.  It is an RXY instruction.