sure to suspend the thread (if necessary) on mac/win32 before 
reading the VM state.

Avoid dealing with signals delivered to non-VM threads on 
linux no matter if we're profiling or not.
Review URL: http://codereview.chromium.org/3845006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5641 ce2b1a6d-e550-0410-aec6-3dcde31c8c00