Some plans for next engine release

Currently I'm refactoring the GUI subsystem. This will allow more flexibility, better code readability, easier debugging, and even less memory usage.

The engine will receive better PNG support, and being able to access PNG's per-index transparency support for indexed images, I might also be able to add some GIF and TIFF support down the line.

One of the libraries the engine uses for rendering now received an ARM port, meaning it'll soon be able to run on Raspberry Pi 2 and above, also on other boards with SoCs supporting NEON, not to mention it opens the door to mobile platforms (D runs pretty well on Android, and some experimented with it on iOS). While at the moment I can't test it on SBCs, I'll look into making it able to run on Android.

The editor will receive a toolbar, also I plan to add some basic object handling (sprites most likely come later).