extract channel count constants from loops

These values are constant, but Clang has some trouble noticing that,
especially if the loop body is complex enough. This prevents it from
noticing places where vectorization is possible (and desirable).
Signed-off-by: Steven Noonan <steven@uplinklabs.net>

research/miniaudio_engine.h

@@ -9320,6 +9320,8 @@ MA_API ma_result ma_spatializer_process_pcm_frames(ma_spatializer* pSpatializer,
         float gain = 1;
         ma_uint32 iChannel;
         float channelGainsOut[MA_MAX_CHANNELS];
+        const ma_uint32 channelsOut = pSpatializer->config.channelsOut;
+        const ma_uint32 channelsIn = pSpatializer->config.channelsIn;
 
         /*
         We'll need the listener velocity for doppler pitch calculations. The speed of sound is
@@ -9520,12 +9522,12 @@ MA_API ma_result ma_spatializer_process_pcm_frames(ma_spatializer* pSpatializer,
         be +1 on the X axis. A dot product is performed against the direction vector of the channel and the normalized
         position of the sound.
         */
-        for (iChannel = 0; iChannel < pSpatializer->config.channelsOut; iChannel += 1) {
+        for (iChannel = 0; iChannel < channelsOut; iChannel += 1) {
             channelGainsOut[iChannel] = gain;
         }
 
         /* Convert to our output channel count. */
-        ma_convert_pcm_frames_channels_f32((float*)pFramesOut, pSpatializer->config.channelsOut, pChannelMapOut, (const float*)pFramesIn, pSpatializer->config.channelsIn, pChannelMapIn, frameCount);
+        ma_convert_pcm_frames_channels_f32((float*)pFramesOut, channelsOut, pChannelMapOut, (const float*)pFramesIn, channelsIn, pChannelMapIn, frameCount);
 
         /*
         Calculate our per-channel gains. We do this based on the normalized relative position of the sound and it's
@@ -9538,7 +9540,7 @@ MA_API ma_result ma_spatializer_process_pcm_frames(ma_spatializer* pSpatializer,
             unitPos.y *= distanceInv;
             unitPos.z *= distanceInv;
 
-            for (iChannel = 0; iChannel < pSpatializer->config.channelsOut; iChannel += 1) {
+            for (iChannel = 0; iChannel < channelsOut; iChannel += 1) {
                 float d = ma_vec3f_dot(unitPos, g_maChannelDirections[pChannelMapOut[iChannel]]);
 
                 /*
@@ -9606,7 +9608,7 @@ MA_API ma_result ma_spatializer_process_pcm_frames(ma_spatializer* pSpatializer,
         }
 
         /* Now we need to apply the volume to each channel. */
-        ma_apply_volume_factor_per_channel_f32((float*)pFramesOut, frameCount, pSpatializer->config.channelsOut, channelGainsOut);
+        ma_apply_volume_factor_per_channel_f32((float*)pFramesOut, frameCount, channelsOut, channelGainsOut);
 
         /*
         Before leaving we'll want to update our doppler pitch so that the caller can apply some