- Separated the linedef activation types into a bit mask that allows combination

of all types on the same linedef. Also added a 'first side only' flag. This
  is not usable from Hexen or Doom format maps though but in preparation of
  the UDMF format discussed here:
  http://www.doomworld.com/vb/source-ports/43145-udmf-v0-99-specification-draft-aka-textmap/
- Changed linedef's alpha property from a byte to fixed point after seeing that
  255 wasn't handled to be fully opaque.
- fixed a GCC warning in fmodsound.cpp 

SVN r954 (trunk)

src/p_buildmap.cpp

@@ -525,11 +525,11 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 		{
 			if (walls[i].cstat & 512)
 			{
-				lines[j].alpha = 255/3;
+				lines[j].Alpha = FRACUNIT/3;
 			}
 			else
 			{
-				lines[j].alpha = 255*2/3;
+				lines[j].Alpha = FRACUNIT*2/3;
 			}
 		}
 		if (walls[i].cstat & 1)