[Rewrite] Make audio source respect file boundaries

[FreeApp2014]

The audio source callback will only check for looping on every call. In case there is not enough samples left in file to fit the frame, it will over-read the buffer, causing silence or garbage noises to be output for a split second, making the loop sound broken.

The looping check should also include the current read too, to reset counter in the middle of reading, so the loop is perfectly smooth.

[FreeApp2014]

Fixed in 7d18825