This change adds a data-flow pass to statically determine
if a variable contains a primitive type.

It requires building the flow graph and computing reaching
definitions as pre-requisites. The analysis annotates all
VariableProxy nodes with the result.

Review URL: http://codereview.chromium.org/1132005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4224 ce2b1a6d-e550-0410-aec6-3dcde31c8c00