Also changed api Wrap function to only wrap suitably small pointers as Smis.
Added Smi validity check and factory meethod for intptr_t.

Review URL: http://codereview.chromium.org/113023


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00