We leave room for all registers on the stack so we have to add a bit.

This is not nicely factored and I need to do that. This will fix the breakage and I
will fix the rest on Monday.

TBR=lrn@chromium.org

Review URL: http://codereview.chromium.org/6544017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6857 ce2b1a6d-e550-0410-aec6-3dcde31c8c00