Quick: Use 16-bit conditional branch in Thumb2.

We were using the 32-bit version because the compilation
time impact of having to change the instruction length and
reassemble instructions when the target is out of range was
too high. However, the assembly phase has been rewritten
since making that decision and the compile time impact is
now insignificant, so we prefer to save space.

Change-Id: Ib90f90d3f4e0c4e310267af272e3b16611026bbe