MIPS: Leaving a generator via an exception causes it to close.

Port 757f400246dc45f889cdc0848094c417e44b8854
Port r25297

BUG=v8:3096
LOG=Y
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/716183004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25304 ce2b1a6d-e550-0410-aec6-3dcde31c8c00