* Add new pg_dbinfo options "dbname", "user", "pass", "host", "port",
"options", "status", "transaction_status", "error_message",
"needs_password", "used_password", "used_ssl" to provide Tcl access
to libpq connection parameter values established at connection time.
* Fixed bug where pg_dbinfo would get a segmentation violation if passed
an invalid connection handle.
* Removed arrVar variable and setting of it in Pg_result because it
didn't do anything.
* Added result callback for async queries via pg_sql. Based on code from Miguel Sofer. I
had this code laying around and thought I had already committed, but turned out no.
