UnaPACK adaptation for GBZ80

Original version: https://gitlab.com/ivagor/unapack

May be used with GBDK/GBDK-2020 v.4.1 and higher

Decompressor for aPLib

http://www.ibsensoftware.com/products_aPLib.html

But there is better compressor apultra

https://github.com/emmanuel-marty/apultra