Changed ACS script state checking into a single switch.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2393 86ba831e-150c-0410-ab35-e06eaae15ed9
Split up T_MovePlane megafunction into separate routines that move a floor or a ceiling either up or down, and two routines which will choose the proper direction handler for a given plane type for places where direction is a variable or thinker member.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2394 86ba831e-150c-0410-ab35-e06eaae15ed9