Fix IR control flow after a throw statement.

Fix IR control flow after a throw statement.

A throw statement in a try block will now jump to the catch/finally, and
a throw statement outside will jump to the exit block. This follows what
happens during run-time, which fixes liveness issues with the
return-temp of calls to builtin_create_exception_handler.

Change-Id: I70f14f03f0431d3fc962c22984d4f486a1d81c7d
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>