This adds the following flags:

  * MA_SOUND_FLAG_LOOPING
  * MA_RESOURCE_MANAGER_DATA_SOURCE_FLAG_LOOPING

These can be used to initialize sounds and resource managed data
sources to loop by default. This is the recommended way to enable
looping for streams. The `isLooping` config option in
`ma_sound_config` and `ma_resource_manager_data_source_config` has been
deprecated. If you are using those, you should switch to the new flag
or else you'll get compiler errors when upgrading to a future version.