Layout scheduling weirdness

[dblohm7]

Form and Event have this weird thing where they are trying to track pending events and suspending layout until no more events are pending.

This is really weird and could be much cleaner by moving layout dispatch to the main event loop: if a layout is pending, we do a PeekMessage instead of a GetMessage until the message queue is empty, and then dispatch the layout.

[dblohm7]

Closely related to #33. It probably makes sense to fix this in the same PR.