Test: audit gui_throttle.c

[aurelienpierre]

1. the throttle manager should accumulate the user inputs it can't process straight away (because history is locked, for example),
2. the throttle manager should empty its queue as soon as history is unlocked (perhaps setting GUI rendering pipes in paused mode when it starts the queue and unset it when it stops),
3. masks interactions should probably put the pipeline in realtime mode (same as drawlayer.c) to shift the priority of pipe re-rendering from "wait the last event" to "best effort/display ASAP".

[aurelienpierre]

Gone as part of GUI refactoring.