Drop from a member name the prefix that classified it

[estebanzimanyi]

A method's ooName is its function name with the class's token dropped, and the
token tried is the class's own lower-cased name. A class whose C prefix is
something else keeps that prefix in every member: Geometry is reached by
geom_*, Geography by geog_* and GeomSet by geoset_*, so their members
read geomBuffer, geogFromHexewkb, geosetStartValue — the class named
twice, once by the receiver and once inside the call.

The classifier already knows which prefix matched, since that is how it chose
the class, so the name drops that prefix too, longest match first. 55 members
across those three classes lose it and no class ends up holding two methods of
one name. One token goes, not every repetition of it: set_set_subspan keeps
its setSubspan, the inner set being part of what the member says.

Stacks on #124.