Rustbound Magic XSkills Compatibility

Adds combats XPs for Rustbound Magic mobs when using XSkills Fork: killing drones / sentries / ravagers / sentinels / titans / colossus now gives you combat XP (for anyone, you don't need to be a Rustmage).

I forgot about the Rustmage class support when making this mod, but XSkills new classes exp added support for it (specific XP multipliers adapted for this specific class), so they are complementary.

This is my first time trying to mod anything, please be nice.