Optimizing/ARM: Fix CmpConstant().

CMN updates flags based on addition of its operands.
Do not confuse the "N" suffix with bitwise inversion
performed by MVN.

Also add more special cases analogous to AddConstant()
and use CmpConstant() more in code generator.

Change-Id: I0d4571770a3f0fdf162e97d4bde56814098e7246
6 files changed