Prevent possible crash on pages with iframes.

In some cases, setupFrame() has not been invoked (due to the queued
signal-slot connection) after the frame is destroyed and thus leads
to the crash. We prevent this from happening by making sure it is a
direct connection instead and therefore setupFrame() will be executed
as soon as possible.

Investigation + patch by Vitaliy Slobodin <vitaliy.slobodin@gmail.com>.

http://code.google.com/p/phantomjs/issues/detail?id=947