Continuing register cleanup

Continuing register cleanup

Ready for review.

Continue the process of using RegStorage rather than
ints to hold register value in the top layers of codegen.
Given the huge number of changes in this CL, I've attempted
to minimize the number of actual logic changes.  With this
CL, the use of ints for registers has largely been eliminated
except in the lowest utility levels.  "Wide" utility routines
have been updated to take a single RegStorage rather than
a pair of ints representing low and high registers.

Upcoming CLs will be smaller and more targeted.  My expectations:
   o Allocate float double registers as a single double rather than
     a pair of float single registers.
   o Refactor to push code which assumes long and double Dalvik
     values are held in a pair of register to the target dependent
     layer.
   o Clean-up of the xxx_mir.h files to reduce the amount of #defines
     for registers.  May also do a register renumbering to bring all
     of our targets' register naming more consistent.  Possibly
     introduce a target-independent float/non-float test at the
     RegStorage level.

Change-Id: I646de7392bdec94595dd2c6f76e0f1c4331096ff