Added necessary code to initialize Top::js_entry_sp value.
Renamed 'test-log-ia32' test to 'test-log-stack-tracer' and enabled it in 64-bit version.

Review URL: http://codereview.chromium.org/160446


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2597 ce2b1a6d-e550-0410-aec6-3dcde31c8c00