[Audio] Backporting Yellow's audio engine into Pokered

[jojobear13]

I have recently succeeded in backporting the updated audio engine from Yellow version into Pokered and wanted to share the code. This will make the audio updater run a bit better and free up lots of space in the audio banks. If backporting color from Yellow, this will also alleviate the audio lag that is caused. Finally, this adds the sound mixing options from Yellow version; press SELECT on the options screen to change between mono, earphone 1, earphone 2, and earphone 3.

Here is the difference report for all the changes. You can ignore bg_map_attributes.asm unless you are also backporting the color from Yellow version.