[SystemZ] set 'guessInstructionProperties = 0' and set flags as needed.
This has proven a healthy exercise, as many cases of incorrect instruction
flags were corrected in the process. As part of this, IntrWriteMem was added
to several SystemZ instrinsics.
Furthermore, a bug was exposed in TwoAddress with this change (as incorrect
hasSideEffects flags were removed and instructions could now be sunk), and
the test case for that bugfix (r319646) is included here as
One temporary test regression (one extra copy) which will hopefully go away
in upcoming patches for similar cases:
Review: Ulrich Weigand.