- added Xaser's reactiontime for ACS and DECORATE expression patch.


git-svn-id: http://mancubus.net/svn/hosted/zdoom/zdoom/trunk@4222 a95907f1-e10c-0410-b46f-9e587ccb1026
- Instead of setting the default skybox in every sector without an explicit skybox set, set it
  once in the level struct and then use that for sectors with a NULL skybox. This fixes zpack's
  E2M3 so that when it removes its sector stacks, you will get the default skybox in their
  place, since stacked sectors and skyboxes use the same pointers in a sector.

git-svn-id: http://mancubus.net/svn/hosted/zdoom/zdoom/trunk@4224 a95907f1-e10c-0410-b46f-9e587ccb1026