Properly reset external catcher if exception couldn't be externally caught.

Properly reset external catcher if exception couldn't be externally caught.

We can wrongly assume that exception which is not intended to be caught
by external try/catch should be caught if this exception inherits
external catcher from some previous exception.  To prevent that,
clear external catcher when processing exceptions which cannot be
externally caught.

BUG=v8:1184
TEST=test/mjsunit/regress/regress-1184.js

Review URL: http://codereview.chromium.org/6538081

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6905 ce2b1a6d-e550-0410-aec6-3dcde31c8c00