Hendrik Leppkes:
	- List all used WoW API functions as allowed globals for the FindGlobals script
	- Add migration code for the new spell overlays
	- Don't register for events which are not used
	- Replace Blizzards OverlayGlow with our own to avoid potentially tainting the overlay glow storage.
	- Handle more events that require a button update
	- Update copyright header
	- Upvalue Lua built-ins
	- Fix variable name when assigning item links to buttons
