[MacPorts] #58620: Add postgresql96 variant to libpqxx port

[MacPorts]

#58620: Add postgresql96 variant to libpqxx port
--------------------------+--------------------
  Reporter:  angelog0     |      Owner:  (none)
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  libpqxx      |
--------------------------+--------------------
Changes (by jmroot):

 * type:  defect => enhancement
 * port:   => libpqxx


-- 
Ticket URL: <https://trac.macports.org/ticket/58620#comment:1>
MacPorts <https://www.macports.org/>
Ports system for macOS