Fix a mips-specific CallCFunction assertion, when checking for valid
frames on the stack. We fake it with AllowExternalCallThatCantCauseGC().

Landing http://codereview.chromium.org/7932010/ for Paul Lind.


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9315 ce2b1a6d-e550-0410-aec6-3dcde31c8c00