Remove the pEngine parameter from all ma_sound_group_*() APIs.

Previously you could set the group to NULL in which case the master
group would be used, but this has now changed and the group parameter
can never be NULL. Use ma_engine_get_master_sound_group() to retrieve
the master sound group.

research/ma_engine.c

@@ -46,6 +46,7 @@ int main(int argc, char** argv)
 
 
 #if 1
+    loadNotification.cb.onSignal = on_sound_loaded;
     loadNotification.pSound = &sound;
 
     result = ma_sound_init_from_file(&engine, argv[1], MA_DATA_SOURCE_FLAG_DECODE | MA_DATA_SOURCE_FLAG_ASYNC | MA_DATA_SOURCE_FLAG_STREAM, &loadNotification, NULL, &sound);
@@ -57,9 +58,9 @@ int main(int argc, char** argv)
 
     /*ma_data_source_seek_to_pcm_frame(sound.pDataSource, 5000000);*/
 
-    //ma_sound_group_set_pan(&engine, NULL, -1);
-    //ma_sound_group_set_pitch(&engine, NULL, 1.0f);
-    //ma_sound_group_set_start_delay(&engine, NULL, 2000);
+    //ma_sound_group_set_pan(ma_engine_get_master_sound_group(&engine), -1);
+    //ma_sound_group_set_pitch(ma_engine_get_master_sound_group(&engine), 1.0f);
+    //ma_sound_group_set_start_delay(ma_engine_get_master_sound_group(&engine), 2000);
     
     /*ma_sound_set_volume(&sound, 0.25f);*/
     //ma_sound_set_pitch(&sound, 2.0f);
@@ -74,7 +75,7 @@ int main(int argc, char** argv)
     ma_sleep(2000);
     printf("Stopping...\n");
     ma_sound_stop(&sound);
-    //ma_sound_group_stop(&engine, NULL);
+    //ma_sound_group_stop(ma_engine_get_master_sound_group(&engine));
 #endif
 
 #if 1
@@ -99,7 +100,7 @@ int main(int argc, char** argv)
             pitchStep = -pitchStep;
         }
 
-        //ma_sound_group_set_pitch(&engine, NULL, pitch);
+        //ma_sound_group_set_pitch(ma_engine_get_master_sound_group(&engine), pitch);
         ma_sound_set_pitch(&sound, pitch);
         printf("Pitch: %f\n", pitch);