Add QEMU audio pseudo-encoding support.

[ayunami2000]

Let me know if the defaults or coding styles need work!

Notice: I did not add any tests, but I did test it (well, an earlier version, before I added the ability to configure channel count and frequency) with my application and it worked.

To test, use something like:

@echo off
"C:\Program Files\qemu\qemu-system-x86_64.exe" -L "C:/Program Files/qemu" -vnc :0 -usbdevice tablet -boot d -m 1024M -cdrom geexbox-3.1-x86_64.iso -vga vmware -device intel-hda -device hda-output

or

qemu-system-x86_64 -vnc :0 -usbdevice tablet -boot d -m 1024M -cdrom geexbox-3.1-x86_64.iso -vga vmware -device intel-hda -device hda-output

^above tests use GeeXboX OS for audio tests: https://archiveos.org/geexbox/

OH, last thing: I used tabs, not spaces, feel free to change them back! And, please test it yourself to make sure it works on your end too!!

[ayunami2000]

Update: The frequency value does not seem to actually change the returned audio's frequency, I'm not really sure why. Let me know where I may have messed up.

Edit: Turns out I had to reorder some parts, remind me to push the changes I made to my PR.