[MacPorts] #68013: mp4v2: Switch to maintained fork, update to 2.1.3

[MacPorts]

#68013: mp4v2: Switch to maintained fork, update to 2.1.3
------------------------+--------------------
 Reporter:  ryandesign  |      Owner:  (none)
     Type:  update      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:
 Keywords:              |       Port:  mp4v2
------------------------+--------------------
 We are using an unmaintained fork of mp4v2 with
 [https://github.com/TechSmith/mp4v2/issues/47 known problems]. In that
 issue, it is pointed out that we might switch to
 [https://github.com/enzo1982/mp4v2 this new maintained fork] as other
 distributions have done. This is a good idea. Since this switch will
 decrease the `version` from 4.1.3 to 2.1.3, the `epoch` must once again be
 increased. Before committing any such switch, I recommend to rebuild and
 test any port that uses mp4v2 to verify that it still finds mp4v2 and
 works. Read the [changeset:799e13d755088c872e7cb46b2aff978a907d5260
 /macports-ports commit message] from when we downgraded to version 4.1.3
 for some background.

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Ticket URL: <https://trac.macports.org/ticket/68013>
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