Peter M. Groen / openbr

A way to avoid deadlocks when using stream inside a distribute transform

Since we no longer put Stream threads on the global thread pool, the previous
changes are unnecessary.

Also, in distribute, set up the QFutureSyncrhonizer with futures in the
opposite order. In Qt 5.1, the waiting thread will wait for each future in the
order they are added to the synchronizer, and thread execution will proceed
in the same order. This prevents the waiting thread from every doing anything
besides waiting. Reversing the QFuture order (so that it is the opposite of
execution order) allows the waiting thread to steal work as intended

Don't use the global thread pool for streams. Micro-managing the global thread
pool's active thread count has proven infeasible, therefore in order to avoid
thread based deadlocks, we don't use the global thread pool. Instead, we share
thread pools across sibling Stream transforms.

Misc. code cleanup and better last frame detection.