V4 ARM JIT: make CONFIG+=disassembler work on ARM.

Change-Id: I164813c8939849e63103c447a7f64699003d00da
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
V4 JIT: move registers for regalloc out of method.

This is a clean-up: by moving the description of the registers available
for allocation out of the run method, the method gets easier to read,
and the lists are easier to extend when adding more platforms.

Change-Id: I840a15cda0e02488b7e038aa23cedd23508ed736
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
V4 JIT: enable register allocator on Linux/ARM.

Change-Id: Ieab86edebcc265063904e78c8c8d0014ace64199
Reviewed-by: Lars Knoll <lars.knoll@digia.com>