Thumb2 Backend: Make arithmetic instructions set condition codes by default

Thumb2 Backend: Make arithmetic instructions set condition codes by default

Most arithmetic instructions can either set the condition codes or
not. With Thumb2, most 2-byte encodings require the condition codes
to be set.
This change allows clients to pass SetCC, LeaveCC, or DontCareCC for
arithmetic instructions including MOV. DontCareCC is the
default. This is equivalent to SetCC except for some multiplication
instructions where it is LeaveCC.
test-disasm-arm.cc is disabled. This test need to be rewritten for the new defaults.

This is the 10th patch for the Thumb2 Backend. 
Previous patch: https://codereview.chromium.org/24792002/
Next patch: https://codereview.chromium.org/24795002/

BUG=none
TEST=none