- fixed incorrect -= operators in vectors.h

git-svn-id: http://mancubus.net/svn/hosted/zdoom/zdoom/trunk@4138 a95907f1-e10c-0410-b46f-9e587ccb1026
- ...now where did that 'F' come from...?

git-svn-id: http://mancubus.net/svn/hosted/zdoom/zdoom/trunk@4139 a95907f1-e10c-0410-b46f-9e587ccb1026
- Add support for user variables on things in UDMF maps. If you include an actor's user variable
  in its UDMF thing definition, that user variable will be set to the desired value for that
  actor when the map is loaded.

git-svn-id: http://mancubus.net/svn/hosted/zdoom/zdoom/trunk@4140 a95907f1-e10c-0410-b46f-9e587ccb1026