JIT: Combine add with shift.

Optimize logical shift for ARM JIT.
Whenever logical shift is followed by an add,
try to replace it with an add capable of performing
the shift in the same instruction.

This improves performance for usecases
involving code executing in Dalvik.

Change-Id: I3cb807b6d6ef4b053a19e2703676a93a930eb963
Signed-off-by: Patrik Ryd <patrik.ryd@stericsson.com>