context of the expressions they label.  Introduce an "unintialized"
location to catch failure to assign any location at all.

Changed the object literal initialization on ARM to use a Store IC in
the same cases where it did on the other platforms.  This was required
because the location of the literal property name is given an
"unitialized" location.

Review URL: http://codereview.chromium.org/339045

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3171 ce2b1a6d-e550-0410-aec6-3dcde31c8c00