Proxies: Make 'with' work, plus minor other fixes

Also fixes internal exception handling in several places of the runtime.

R=yangguo@chromium.org
BUG=v8:1543

Review URL: https://codereview.chromium.org/19384004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15781 ce2b1a6d-e550-0410-aec6-3dcde31c8c00