Enhancement: containsVertex function

[mtnclimb]

A containsVertex function might be a useful addition.

int containsVertex(Geometry geom, double x, double y)

I geom contains a vertex with location (x,y), returns the index of that vertex. Otherwise returns -1. For geometrys which contain more than one coordinate sequence, the index is the cumulative index over all coordinate sequences.

This can be implemented as a fast linear scan of all vertices in the geometry.