2.6 Send and get with more arguments

Though the principal predicates for invoking behaviour are send/2 and get/3, XPCE provides an alternative using send/[2-12] and get/[3-13]. The following goals are all identical.

send(Box, width(100))send(Box, width, 100)
get(Point, distance(point(10,10), D)get(Point, distance, point(10,1), D)

This alternative is provided for compatibility to pre-5.0 versions as well as to support users that dislike the new-style send/2 and get/3. It is realised using goal_expansion/2 and thus poses only a small compile-time overhead.