Fix issues with WavStream looping (Flac, Wav & MP3)

[pgrAm]

There were a few issues with WavStreams and looping, fixed here

• WavStreamInstance::seek would always take the branch for OGG leading other formats to stop playing after one loop
• The sample copying loop was using the incorrect pitch, aSamplesToRead instead of aBufferSize, causing garbage noise at the end of a loop when aSamplesToRead != aBufferSize
• logic for WavStreamInstance::hasEnded() differed from that of WavInstance::hasEnded()