[MacPorts] #53747: lmdb : update to 0.9.19

[MacPorts]

#53747: lmdb : update to 0.9.19
---------------------+----------------------
  Reporter:  RJVB    |      Owner:
      Type:  update  |     Status:  new
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:  haspatch
      Port:  lmdb    |
---------------------+----------------------

Comment (by ryandesign):

 The `platforms` statement serves to inform the user what platforms the
 port is believed to work on. MacPorts doesn't check this value, merely
 shows it to the user.

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Ticket URL: <https://trac.macports.org/ticket/53747#comment:4>
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