surrounding context to figure out if the variable could be global.  If
the variable could be global we check context extension objects at
runtime and use a global LoadIC if no variables have been introduced
by eval.

Fix crash bug when loading function arguments from inside eval.  The 
shadowed variable in the DYNAMIC_LOCAL case does not rewrite to a slot in 
that case.

Review URL: http://codereview.chromium.org/28027

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1348 ce2b1a6d-e550-0410-aec6-3dcde31c8c00