use dr_wav to implement wav input

[chocolate42]

• 16 bit has been implemented and seems to work, more testing required. Possible endian issue if on a big-endian device, untested
• No other input depth works (32 bit might but untested), possibly because of the conversion in drwav_read_pcm_frames_s32. Tried doing it manually with drwav_read_pcm_frames but not successful yet
• drwav doesn't seem to have a convenient way to handle FILE* input, so piping might be a pain to implement