Fuse long and FP compare & condition on ARM in Optimizing.

Also:
- Stylistic changes in corresponding parts on the x86 and
  x86-64 code generators.
- Update and improve the documentation of
  art::arm::Condition.

Bug: 21120453
Change-Id: If144772046e7d21362c3c2086246cb7d011d49ce
9 files changed