bump version number
buildings: define large zone structures in tiles.rc
buildings: implement zonePlopNew() to place a zone using info in tiles.rc

Take note that the argument given to this function is not the upper-left
tile value, but rather the "zone" tile for the building.
buildings: replace callers of zonePlop() with calls to zonePlopNew()
buildings: remove obsolete zonePlop()
buildings: rename zonePlopNew() to zonePlop()