[IMPROVEMENT] Updated libGPAC to 0.7.1 (#778)

[thefar8]

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Have updated libGPAC from v0.6.2 to the latest version on their GitHub

Any feedbacks would be appreciated :)

[canihavesomecoffee]

Linux seems to be fully broken:

https://sampleplatform.ccextractor.org/test/961

Failed to build using builddebug
Failed to build using autoconf
(cmake was already broken)

Please check this out and fix this, this will be necessary to merge this.

[thefar8]

Wait
I have to change the whole .c in GPAC too

[cfsmp3]

Please reopen (or send a new one) when it's ready for review.