More MIPS fixes. Most basic tests pass.

IntMath works now. The only basic tests that aren't working are
ReferenceMap and StackWalk.

In this change:
- Fixed argument passing for compare float/double.
- Set method stubs for long multiply/divide/remainder.
- Store gp value on stack and reload after function call to preserve
  value for exception delivery.
- Fixed argument passing to artThrowStackOverflowFromCode.
- Fixed assembly for unsigned shift right long.

Change-Id: I6e77454905c3620c9cfd1c089200a8dbe530df2e