Upgrade to love2d 11.x

[satyanash]

This game indicates it was made for version '0.10.0' of LOVE.
It may not be compatible with the running version (11.3).

Game was built for love2d 0.10.0 (Super Toast) which was released in 2015.
We should consider upgrading to 11.x (Mysterious Mysteries) which is the latest version in 2019.

Game breaks on 11.3 with the following exception:

LOVE - Warning: hawk/application.lua:11: Using deprecated function love.filesystem.exists (replaced by love.filesystem.getInfo)
Error: [string "boot.lua"]:302: Failed to initialize filesystem: already initialized
stack traceback:
	[C]: in function 'init'
	[string "boot.lua"]:302: in function <[string "boot.lua"]:296>
	[C]: in function 'xpcall'
	[string "boot.lua"]:782: in function <[string "boot.lua"]:780>
	[C]: in function 'xpcall'
make: *** [Makefile:31: run] Error 1

[niamu]

There is already an open PR that is in progress for this issue (#2571). The problem is that LÖVE breaks significant APIs across major versions and the changes needed to resolve this are extensive. So far no one has completed this work, but we'd welcome more help.

[satyanash]

#2571 is actually playable for the most part. There seem to be some issues with a few tiles here and there.
But yes, it's a very large PR to manage.
It might make sense to break down the transition to 11.x into smaller ones which (hopefully) will be backwards compatible with 0.10.x.
Could have a separate branch running for 11.x migration; in any case master isn't very busy these days so rebasing onto it should be straightforward.