Add some more instruction support to optimizing compiler.

This adds a few more DEX instructions to the optimizing compiler's
builder (constants, moves, if_xx, etc).

Also:
* Changes the codegen for IF_XX instructions to use a condition
  rather than comparing a value against 0.
* Fixes some instructions in the ARM disassembler.
* Fixes PushList and PopList in the thumb2 assembler.
* Switches the assembler for the optimizing compiler to thumb2
  rather than ARM.

Change-Id: Iaafcd02243ccc5b03a054ef7a15285b84c06740f