Clean up and prevent unnecessary qualifiers to self

By "unnecessary qualifiers to self", I mean something like using the
'game.' qualifier for a variable on the Game class when you're inside a
function on the Game class itself. This patch is to enforce consistency
as most of the code doesn't have these unnecessary qualifiers.

To prevent further unnecessary qualifiers to self, I made it so the
extern in each header file can be omitted by using a define. That way,
if someone writes something referring to 'game.' on a Game function,
there will be a compile error.

However, if you really need to have a reference to the global name, and
you're within the same .cpp file as the implementation of that object,
you can just do the extern at the function-level. A good example of this
is editorinput()/editorrender()/editorlogic() in editor.cpp. In my
opinion, they should probably be split off into their own separate file
because editor.cpp is getting way too big, but this will do for now.

desktop_version/src/Graphics.cpp

@@ -1,3 +1,4 @@
+#define GRAPHICS_DEFINITION
 #include "Graphics.h"
 
 #include <stdio.h>
@@ -2991,16 +2992,16 @@ void Graphics::renderwithscreeneffects()
 {
 	if (game.flashlight > 0 && !game.noflashingmode)
 	{
-		graphics.flashlight();
+		flashlight();
 	}
 
 	if (game.screenshake > 0 && !game.noflashingmode)
 	{
-		graphics.screenshake();
+		screenshake();
 	}
 	else
 	{
-		graphics.render();
+		render();
 	}
 }