Plus use more robust path when formatting messages---work
directly with fixed arrays.

BUG=v8:1107
TEST=test/mjsunit/getter-in-prototype.js,test/mjsunit/regress/regress-1107.js

Review URL: http://codereview.chromium.org/6451004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6689 ce2b1a6d-e550-0410-aec6-3dcde31c8c00