[Pidgin] #17274: port backend-fs to newer api for farstream relay-info property

[Pidgin]

#17274: port backend-fs to newer api for farstream relay-info property
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 Reporter:  bellet                            |       Owner:
     Type:  defect                            |      Status:  new
Milestone:  2.13.0                            |   Component:  libpurple
  Version:  2.12.0                            |  Resolution:
 Keywords:  backend-fs2 farstream relay-info  |
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Comment (by bellet):

 This patch makes modifications conditionally to the value of the
 HAVE_FARSIGHT macro, since the previous relay-info type GValueArray is a
 reminiscence of earlier versions of farstream/farsight:

 [https://gitlab.collabora.com/farstream/farstream/commit/dfcbd4cbcf111d6cfe6c174c4fdb5a9235062cf9#1eaef8555c68c6ddb383cc728a916a8fa4f7632e_333_347]

 But the overall distinction in backend-fs2.c between HAVE_FARSIGHT and not
 HAVE_FARSIGHT (meaning "have farstream") should probably be dropped
 completely.

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Ticket URL: <https://developer.pidgin.im/ticket/17274#comment:1>
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