Fix endless loop when decoding OGGs, #390

In idSampleDecoderLocal::DecodeOGG() `totalSamples` was 1 and
`reqSamples` was 0, which caused an endless loop.. this was caused by
idSoundWorldLocal::ReadFromSaveGame() setting
`chan->openalStreamingOffset` to an odd number, I think due to
`currentSoundTime` being an odd number.
To fix that, I round up `chan->openalStreamingOffset` to a (very) even
number, and to be double-sure I also added a check in DecodeOgg() to
make sure it exits the loop if `reqSamples` is 0.

neo/sound/snd_decoder.cpp

@@ -583,6 +583,16 @@ int idSampleDecoderLocal::DecodeOGG( idSoundSample *sample, int sampleOffset44k,
 		float* samples[2] = { samplesBuf[0], samplesBuf[1] };
 		int reqSamples = Min( MIXBUFFER_SAMPLES, totalSamples / sample->objectInfo.nChannels );
 		int ret = stb_vorbis_get_samples_float( stbv, sample->objectInfo.nChannels, samples, reqSamples );
+		if ( reqSamples == 0 ) {
+			// DG: it happened that sampleCount was an odd number in a *stereo* sound file
+			//  and eventually totalSamples was 1 and thus reqSamples = totalSamples/2 was 0
+			//  so this turned into an endless loop.. it shouldn't happen anymore due to changes
+			//  in idSoundWorldLocal::ReadFromSaveGame(), but better safe than sorry..
+			common->DPrintf( "idSampleDecoderLocal::DecodeOGG() reqSamples == 0\n  for %s ?!\n", sample->name.c_str() );
+			readSamples += totalSamples;
+			totalSamples = 0;
+			break;
+		}
 		if ( ret == 0 ) {
 			int stbVorbErr = stb_vorbis_get_error( stbv );
 			if ( stbVorbErr == VORBIS__no_error && reqSamples < 5 ) {

neo/sound/snd_world.cpp

@@ -1383,6 +1383,11 @@ void idSoundWorldLocal::ReadFromSaveGame( idFile *savefile ) {
 			// make sure we start up the hardware voice if needed
 			chan->triggered = chan->triggerState;
 			chan->openalStreamingOffset = currentSoundTime - chan->trigger44kHzTime;
+			// DG: round up openalStreamingOffset to multiple of 8, so it still has an even number
+			//  if we calculate "how many 11kHz stereo samples do we need to decode" and don't
+			//  run into a "I need one more sample apparently, so decode 0 stereo samples"
+			//  situation that could cause an endless loop.. (44kHz/11kHz = 4; *2 for stereo => 8)
+			chan->openalStreamingOffset = (chan->openalStreamingOffset+7) & ~7;
 
 			// adjust the hardware fade time
 			if ( chan->channelFade.fadeStart44kHz != 0 ) {