#1 pgConn destruct fails to unregister chan

[Don Porter]

An interactice tclsh session:

% package require tclpq
1.0
% set db [pgConnection #auto dbname=test]
socket: sock3
pgConnection0
% delete object $db
% set db [pgConnection #auto dbname=test]
Tcl_RegisterChannel: duplicate channel names
Abort (core dumped)

Looks to me like the destructor of the
pgConnection object is failing to unregister
the Tcl channel when PQfinish closes the socket.