increase land tex size to 512, which is the current minimum required just to load a hat. On my system max fps rose from 840 to 890 - about 6% change. also a nil check, probably not needed.

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