Signal handler on simulator now retrieve registers from the simulator not from the host machine.

BUG=v8:2621

Review URL: https://codereview.chromium.org/13845014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14235 ce2b1a6d-e550-0410-aec6-3dcde31c8c00