[MANYMAPS] add native map-changing support
Add support for fs_library instead of forcing /Library in fs_game
Fix a mistake by kung (2x strtok initialization)
and allow whitelisting of *Empty.iwd and zzz_*.iwd files (hardcoded, sorry)
Fix double slash and nicer unlink-status
Merge branch 'master' of https://github.com/kungfooman/libcod into new-master