[common] Screen size is auto-determined with SDL 2.0.3

Upstream changeset: https://hg.libsdl.org/SDL/rev/e33b5f7df761

The nemomobile package is SDL 2.0.3 from upstream plus that single
commit cherry-picked to allow proper operation also on Sailfish OS.
[mixer] Use libaudioresource before using audio device
Merge branches 'auto-screen-size' and 'audioresource' into testing