also convert/pngcrush png pictures with 16bit/channel (resulting in 8bit/channel) and repage their layers (as I found out that some of the pics had their layer offset the actual visual area, which makes the picture look blank in gimp)

foreach(dir "Fonts" "Forts" "Graphics" "Locale" "Maps" "Music" "Sounds" "Themes" "Missions" "Names" "misc" "Scripts")
  add_subdirectory(${dir})
endforeach(dir)