psql: add tab completion for \df slash command suffixes

When Who What
2019-09-30 17:58:17 Álvaro Herrera (alvherre) Closed in commitfest 2019-09 with status: Returned with feedback
2019-09-12 19:32:55 Álvaro Herrera (alvherre) New status: Waiting on Author
2019-09-04 06:14:40 Kuntal Ghosh (kuntal_ghosh) Added kuntal_ghosh as reviewer
2019-08-30 05:04:00 Ian Barwick (barwick) Changed targetversion to stable
2019-08-30 05:04:00 Ian Barwick (barwick) Changed authors to Ian Barwick (barwick)
2019-08-30 05:03:31 Ian Barwick (barwick) Attached mail thread 07056421-2c99-9de8-c003-d8b800d5060c@2ndquadrant.com
2019-08-30 05:03:31 Ian Barwick (barwick) Created patch record