Fix release fade-out not being applied

This fixes to bugs leading to clicks on instrument note-off in most
instruments.

The first bug was introduced as part of a refactoring done by Vesa [1]
and caused each note play handle's last buffer being dropped because
the play handles were deleted before being processed in AudioPort.
Thanks to @lleroy for pointing this out. [2]

The second bug / typo has always been there [3] and was a misplaced
parenthesis in Instrument::applyRelease breaking the calculation of the
note-off envelope's start frame, sometimes putting it outside of the
buffer.

Fixes #3086

[1] 857de8d2c8 and related commits
[1] https://github.com/LMMS/lmms/issues/3086#issuecomment-519087089
[2] 02433380c6

src/core/AudioEngine.cpp

@@ -394,6 +394,17 @@ void AudioEngine::renderStageInstruments()
 
 	AudioEngineWorkerThread::fillJobQueue(m_playHandles);
 	AudioEngineWorkerThread::startAndWaitForJobs();
+}
+
+
+
+void AudioEngine::renderStageEffects()
+{
+	AudioEngineProfiler::Probe profilerProbe(m_profiler, AudioEngineProfiler::DetailType::Effects);
+
+	// STAGE 2: process effects of all instrument- and sampletracks
+	AudioEngineWorkerThread::fillJobQueue(m_audioPorts);
+	AudioEngineWorkerThread::startAndWaitForJobs();
 
 	// removed all play handles which are done
 	for( PlayHandleList::Iterator it = m_playHandles.begin();
@@ -424,17 +435,6 @@ void AudioEngine::renderStageInstruments()
 
 
 
-void AudioEngine::renderStageEffects()
-{
-	AudioEngineProfiler::Probe profilerProbe(m_profiler, AudioEngineProfiler::DetailType::Effects);
-
-	// STAGE 2: process effects of all instrument- and sampletracks
-	AudioEngineWorkerThread::fillJobQueue(m_audioPorts);
-	AudioEngineWorkerThread::startAndWaitForJobs();
-}
-
-
-
 void AudioEngine::renderStageMix()
 {
 	AudioEngineProfiler::Probe profilerProbe(m_profiler, AudioEngineProfiler::DetailType::Mixing);

src/core/Instrument.cpp

@@ -186,7 +186,7 @@ void Instrument::applyRelease( sampleFrame * buf, const NotePlayHandle * _n )
 	{
 		for( fpp_t f = (fpp_t)( ( fl > desiredReleaseFrames() ) ?
 				(std::max(fpp - desiredReleaseFrames(), 0) +
-					fl % fpp) : 0); f < frames; ++f)
+					fl) % fpp : 0); f < frames; ++f)
 		{
 			const float fac = (float)( fl-f-1 ) /
 							desiredReleaseFrames();