i.e., don't create a bridge interface and pass it, just pass the
interface to be bridged to and vmnet will create the vmenet and
bridge interfaces

In case there are other network implementations later.

When zero, don't grab the keyboard with the mouse.

When we're idle and nothing is happening on screen, we can save some
host CPU by not having to constantly iterate through the video
memory buffer and send it through SDL just to redraw the same thing
over and over.

This greatly speeds up EtherTalk since we are no longer dropping
additional packets and having to wait and retry them.

When double-clicking fast enough, Mac OS doesn't seem to register
the mouse up and re-mouse-down, despite the 6522 seeing both mouse
events. Add the ability to delay processing mouse events in the SDL
event queue for a small amount of time which seems to fix the issue.

This requires a patched ROM but otherwise works as expected.