avoid data races in rvoice_eventhandler and cleanup
avoid data races in rvoice_eventhandler and cleanup

- an element from the queue might be requested from thread A
- thread A is put to sleep just before he could insert his event and increment queue_stored
- thread B request an element from queue, gets the same as thread A
- thread B commits his changes and increases queue_stored
- thread A wakes up, commits his changes
- event of thread B is lost

FluidSynth/fluidsynth,nezticle/fluidsynth,FluidSynth/fluidsynth,nezticle/fluidsynth,FluidSynth/fluidsynth,nezticle/fluidsynth,nezticle/fluidsynth,FluidSynth/fluidsynth