Include config.h and compat.h in common.h, and include common.h from all source files.
Improve downscaling quality if mipmapping is available. Suggested-by: Giumo Clanjor (哆啦比猫/兰威举) <cjxgm2@gmail.com> Fixes #40 <https://github.com/Genymobile/scrcpy/issues/40> Ref: <https://github.com/Genymobile/scrcpy/issues/40#issuecomment-591917787>