ZOOM_connection_connect() now understands authentication parameters

ZOOM_connection_connect() now understands authentication parameters
embedded in the host string, like this:
	admin:secretpw%localhost:9999/gils
i.e. if there is a "%" sign, then what comes before is taken as a
":"-separated user/password pair.  This is a bit hacky, but necessary
to run zoomtst9 against secured databases, and it's much more general
than just adding authentication parameters to that one program.