Audio: Stop pre-silencing the miniaudio output buffer.

raylib already manually silences the output buffer prior to mixing so
there is no reason to have miniaudio also do it. It can therefore be
disabled via the device config to make data processing slightly more
efficient.

src/raudio.c

@@ -480,6 +480,7 @@ void InitAudioDevice(void)
     config.sampleRate = AUDIO_DEVICE_SAMPLE_RATE;
     config.dataCallback = OnSendAudioDataToDevice;
     config.pUserData = NULL;
+    config.noPreSilencedOutputBuffer = true;    // raylib pre-silences the output buffer manually
 
     result = ma_device_init(&AUDIO.System.context, &config, &AUDIO.System.device);
     if (result != MA_SUCCESS)