The map interface assumed grid maps have values -1, 0, or +1. I extended the interface with a data_range value that allows an interface to inform the subscriber that : -data_range <= FREESPACE < 0, UNKNOWN==0, 0 < OCCUPIED < data_range. Therefore maps can have various beliefs about occupancy instead of being binary in belief or agnostic. E.g., a map may now hold the logodds probability of a cell being occupied.
The patch included fixes playerv to scale images based on the data_range value, fixes the playerc and playerc++ proxies to handle the extra value in the interface, and makes all existing map drivers in the player source set data_range=1 (existing clients that use these drivers will simply ignore the data_range field, but it should stil be set to 1).