added first interface for flood fill
put ff_map inside a struct, function changes
ff_map should go in a struct so we can get the right sizeof without confusion.  There also may be some things (like the target) that we want to store away in that group.  We will assume that we will want to build the ff map at the center first.  We can then translate the target somewhere else since all of the relative positionings stay the same.
added untested ff_compute implementation
modified ff_create to fix build problems
stupid stuff...