Allow using 'help', 'graphics', 'music', 'game', 'key', 'map', and 'obj' everywhere

[InfoTeddy]

Changes:

• Allow using help, graphics, music, game, key, map, and obj everywhere

  This PR makes help, graphics, music, game, key, map, and obj essentially static global objects that can be used everywhere. This is useful in case we ever need to add a new function in the future, so we don't have to bother with passing a new argument in which means we have to pass a new argument in to the function that calls that function which means having to pass a new argument into the function that calls that function, etc. which is a real headache when working on fan mods of the source code.

  Note that this changes none of the existing function signatures, it merely just makes those variables accessible everywhere in the same way script and ed are.

  Also note that some classes had to be initialized after the filesystem was initialized, or else the game would segfault. But C++ would keep initializing them before the filesystem got initialized, because I had to put them at the top of main.cpp, or else they wouldn't be global variables.

  The only way to work around this was to use entityclass's initialization style (which I'm pretty sure entityclass of all things doesn't need to be initialized this way), where you actually initialize the class in an init() function, and so then you do graphics.init() after the filesystem initialization, after doing Graphics graphics up at the top.

  I've had to do this for graphics (but only because its child GraphicsResources grphx needs to be initialized this way), music, and game. I don't think this will affect anything. Other than that, help, key, and map are still using the C++-intended method of having ClassName::ClassName() functions.

Legal Stuff:

By submitting this pull request, I confirm that...

• My changes may be used in a future commercial release of VVVVVV (for
  example, a 2.3 update on Steam for Windows/macOS/Linux)
• I will be credited in a CONTRIBUTORS file for all of said releases, but
  will NOT be compensated for these changes

[TerryCavanagh]

Huh! Yeah, this seems like a useful change, and a good first step towards eventually stabilising this jenga tower of a game (i.e. removing the reference passing stuff from virtually every function in the game).

I can't think of any reason this might cause a problem - any thoughts, @flibitijibibo?

[flibitijibibo]

None I can think of - may be worth checking the Win64 issue after this, it might fix that as a side effect.