Heretic Thing Support at > 33%

I have added the Ghost Golem, Ghost Leader Golem, and Disciple to Eternity, and this brings the total of Heretic mapthing types supported to about 33.5% -- meaning more than a third of the work is done in that respect.

The enemies still awaiting implementation, and reasons they've not been done yet, are as follows:

Knight, Ghost Knight -- projectile requires WINDTHRUST flag
Beast -- projectile requires FIREDAMAGE flag
Ophidian -- projectile 1 requires WINDTHRUST flag
Iron Lich -- fire projectiles require WINDTHRUST, tornadoes require various considerations
Maulotaur -- most of his code is already in the engine from Eternity TC, but it needs adaptation, and the FIREDAMAGE flags on the projectiles
Serpent Rider D'Sparil -- fireballs require WINDTHRUST flag
D'Sparil -- spawned by Serpent Rider D'Sparil
Pods -- require WINDTHRUST, SLIDE flags
Volcanoes -- require FIREDAMAGE flag

Edit: I forgot the Imp and Imp Leader. There's a number of issues with them too, including their "crashstate" they sometimes go into when dying.