[MacPorts] #63060: Update libpst version to 0.6.76

[MacPorts]

#63060: Update libpst version to 0.6.76
------------------------+--------------------
  Reporter:  srirangav  |      Owner:  (none)
      Type:  update     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.7.1
Resolution:             |   Keywords:
      Port:  libpst     |
------------------------+--------------------

Comment (by srirangav):

 I have submitted a pull request through GitHub:

 https://github.com/macports/macports-ports/pull/11290

 I am new to pull requests on GitHub, so I apologize if I have not done it
 properly.

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Ticket URL: <https://trac.macports.org/ticket/63060#comment:2>
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