This tries to propagate exceptions which are externally thrown into
external try-catch handlers before scheduling them. This also allows
embedders to nest external try-catch handlers.

This just relands r11834.

R=svenpanne@chromium.org
BUG=v8:2166
TEST=cctest/test-api/TryCatchNested

Review URL: https://codereview.chromium.org/11299329

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13129 ce2b1a6d-e550-0410-aec6-3dcde31c8c00