AGI: Change the way the mixer volume is handled in the PCjr player

Instead of factoring the volume into the tone attenuation it now scales
the volume table. This way it still uses the full table when playing
at a low volume and therefore keeps the 16 attenuation levels.

Also use kMusicSoundType instead of kSFXSoundType to be coherent with what
the MIDI output is doing (volume for both music and SFX is controlled by
the Music volume slider).

engines/agi/sound_pcjr.cpp

@@ -205,7 +205,6 @@ int SoundGenPCJr::volumeCalc(SndGenChan *chan) {
 				chan->attenuationCopy = attenuation;
 
 				attenuation &= 0x0F;
-				attenuation += (16 - _mixer->getVolumeForSoundType(Audio::Mixer::kSFXSoundType) / 17);
 				if (attenuation > 0x0F)
 					attenuation = 0x0F;
 			}
@@ -475,8 +474,9 @@ int SoundGenPCJr::fillSquare(ToneChan *t, int16 *buf, int len) {
 
 	count = len;
 
+	int16 amp = (int16)(volTable[t->atten] * _mixer->getVolumeForSoundType(Audio::Mixer::kMusicSoundType) / Audio::Mixer::kMaxMixerVolume);
 	while (count > 0) {
-		*(buf++) = t->sign ? volTable[t->atten] : -volTable[t->atten];
+		*(buf++) = t->sign ? amp : -amp;
 		count--;
 
 		// get next sample
@@ -513,8 +513,9 @@ int SoundGenPCJr::fillNoise(ToneChan *t, int16 *buf, int len) {
 
 	count = len;
 
+	int16 amp = (int16)(volTable[t->atten] * _mixer->getVolumeForSoundType(Audio::Mixer::kMusicSoundType) / Audio::Mixer::kMaxMixerVolume);
 	while (count > 0) {
-		*(buf++) = t->sign ? volTable[t->atten] : -volTable[t->atten];
+		*(buf++) = t->sign ? amp : -amp;
 		count--;
 
 		// get next sample