Fix ARM FastISel tests, as a first step to enabling ARM FastISel

ARM FastISel is currently only enabled for iOS non-Thumb1, and I'm working on
enabling it for other targets. As a first step I've fixed some of the tests.
Changes to ARM FastISel tests:
- Different triples don't generate the same relocations (especially
  movw/movt versus constant pool loads). Use a regex to allow either.
- Mangling is different. Use a regex to allow either.
- The reserved registers are sometimes different, so registers get
  allocated in a different order. Capture the names only where this
  occurs.
- Add -verify-machineinstrs to some tests where it works. It doesn't
  work everywhere it should yet.
- Add -fast-isel-abort to many tests that didn't have it before.
- Split out the VarArg test from fast-isel-call.ll into its own
  test. This simplifies test setup because of --check-prefix.

Patch by JF Bastien