Enabling AES-GCM when using external libSRTP version 1.x and 2.0.0

[pjsipbot]

2017-10-05 05:22:09: @trengginas created the issue on trac ticket 2050

Pjsip is bundled with libSRTP 2.1, however users are allowed to use external
libSRTP (see r5656). This ticket will enabled AES-GCM when using external libSRTP specially version 1.x and 2.0.0.

Thanks to Alexander Traud for the patch.

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2017-10-05 05:40:24: @trengginas changed status from new to closed

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2017-10-05 05:40:24: @trengginas set resolution to fixed

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2017-10-05 05:40:24: @trengginas commented

In r5670:
Close #2050: Enabling AES-GCM when using external libSRTP version 1.x or 2.0.0.