Fixes#3017
Thanks to Hercules for the idea and their implementation of it.
This deprecates Windows XP support. If you want to use it to run your server on it, you have to forcefully enable it now.
Since 64bit ticks do not exist on XP, you might encounter some issues that are already fixed on other OS.
Introducing a new constant INFINITE_TICK
Changed current usages in items, npcs and source to use the new and correct constant.
Replaced some invalid usages of INVALID_TIMER and replaced them with the new constant.
* Alphabetically sorted includes.
* Updated copyright and license text to match across all files.
* Removed pragma once define in header files in lieu of ifdef guards.
