Quick compiler: debugging assists

A few minor assists to ease A/B debugging in the Quick
compiler:
   1.  To save time, the assemblers for some targets only
update the object code offsets on instructions involved with
pc-relative fixups.  We add code to fix up all offsets when
doing a verbose codegen listing.
   2.  Temp registers are normally allocated in a round-robin
fashion.  When disabling liveness tracking, we now reset the
round-robin pool to 0 on each instruction boundary.  This makes
it easier to spot real codegen differences.
   3.  Self-register copies were previously emitted, but
marked as nops.  Minor change to avoid generating them in the
first place and reduce clutter.

Change-Id: I7954bba3b9f16ee690d663be510eac7034c93723