Libplot has its own versioning scheme, independent of the scheme used for
numbering the releases of the plotutils package.  The version of libplot in
this directory is 2.0, age=0.  That means

	interface number = 2
	revision = 0
	
	Support for interfaces extending backward by 0 units from current
	interface number, i.e., support only for the interfaces supplied by
	libplot 2.x.  (Earlier interfaces are not supported, because
	they did not use the "pl_" prefix.)
