Used incorrect register for referencing RegExp data, so it always failed
to match the fast case.
When modifiying the object layout, it was possible to make it crash instead.

BUG=v8:1236
TEST=test/mjsunit/regress/regress-1236.js

Review URL: http://codereview.chromium.org/6635041

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7091 ce2b1a6d-e550-0410-aec6-3dcde31c8c00