Interpret the waterlevel value as tenths of a cube.
This makes the waterlevel variable a float value to the user, while the
map file still stores an integer value - but now it is interpreted
differently - for example, a waterlevel value of 123 now means 12.3 cubes
instead of 123. Old map files are converted during loading.
Note: the values of waterlevel and hdr.waterlevel need to be in sync.
DOCREF waterlevel
ac-stef
ea480a7b0c