Instead of generating the following for "100 - x":

  mov r1, #100
  subs r0, r1, r0

this patch makes Crankshaft generate this:

  rsbs r0, r0, #100

thus saving a register and a mov.

BUG=

Review URL: https://chromiumcodereview.appspot.com/11308040
Patch from Hans Wennborg <hans@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13017 ce2b1a6d-e550-0410-aec6-3dcde31c8c00