stack for now.  Next step is probably fixing the binary
op stubs so they can take swapped registers and fixing
the deferred code so it doesn't insist that all registers
except the two operands are flushed.  Generates slightly
worse code sometimes because the peephole push-pop
elimination gets confused when we don't use the same
register all the time (the old code used r0 always).
Review URL: http://codereview.chromium.org/1604002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4368 ce2b1a6d-e550-0410-aec6-3dcde31c8c00