Change compilation of assignment expressions in the ia32 code
generator to no longer use the Reference helper class.  This gives us
more explicit control over which subexpressions are evaluated and
when.

Review URL: http://codereview.chromium.org/643001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3899 ce2b1a6d-e550-0410-aec6-3dcde31c8c00