Clipping wall the farthest of the camera, in world dimensions

Default at 10000.0 but this one should be adapted to each context.

Property definitions

gamnit $ EulerCamera :: far
	# Clipping wall the farthest of the camera, in world dimensions
	#
	# Default at `10000.0` but this one should be adapted to each context.
	var far = 10000.0 is writable
lib/gamnit/cameras.nit:64,2--67,30