Adirelle:
	- Experimental Masque support.
	- Have all overlays send debug messages to the same channel.
	- Moved code around in Display.lua and normalized theme handling.
	- Changed (and renamed) the texture widgets used for highlight and darken/lighten overlay.
Sergio Álvarez:
	- added a thin border media similar to square corners, without the corners
Adirelle:
	- README updates.
	- Made tests/globals.sh executable.
	- Globally fixed the globals.
	- Added an automated test to check for leaking globals, using Mikk's globals.lua.
	- Update README.md
