Allow definition of class-methods.

[skx]

We now have support for calling things like:

 "Steve".count("e");

We should allow the user to define similar methods in pure Monkey, rather than in go.

The initial case should allow:

 function TYPE.name( self );

Where TYPE is string, array, hash, etc. It might be I have to cheat and use ":" instead of "." to simplify life, but I could live with that. The important thing is that it is possible at all.