The map iterator now has init/finish capability, making it possible to
write scripts that aggregate data over multiple map files. One such example
calculates some statistics, the other loads art metadata and looks for
red walls with non-pow2 ysize tiles.
git-svn-id: https://svn.eduke32.com/eduke32@2814 1a8010ca-5511-0410-912e-c29ae57300e0
