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 1.6, age=1.  That means

	interface number = 1
	revision = 6
	
	Support for interfaces extending backward by 1 units from current
	interface number, i.e., support for the interfaces supplied by
	libplot 1.x, and 0.x.
