(generic state inside V8) in the API to allow the V8 shell to run all
the mjsunit tests with heap protection on.

These state changes are only taken when built with
ENABLE_HEAP_PROTECTION.  The two states OTHER and EXTERNAL are treated
the same because we will not properly reenter OTHER through the API.
Review URL: http://codereview.chromium.org/56060

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1643 ce2b1a6d-e550-0410-aec6-3dcde31c8c00