Support for items that spawn at a random spot out of a collection of all things of that type in a map. Added definitions for Heretic fire mace pickup. Milestone: ALL Heretic objects with doomednums are now implemented.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2635 86ba831e-150c-0410-ab35-e06eaae15ed9