ARI: Correct segfault with /variable calls are missing ?variable parameter.

Both /asterisk/variable and /channel/{channelId}/variable requires a
?variable parameter to be passed into the query. But we weren't checking
for the parameter being missing, which caused a segfault.

All calls now properly return 400 Bad Request errors when the parameter
is missing. The Swagger api-docs were updated accordingly.

(closes issue ASTERISK-22273)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@397306 f38db490-d61c-443f-a65b-d21fe96a405b
Set 14400 as the default max bit rate if T38MaxBitRate is not specified

If an endpoint fails to include the T38MaxBitRate attribute during negotiation,
Asterisk will negotiate a bit rate of 2400 instead of the ITU recommended
bit rate of 14400. This patch fixes this by making AST_T38_RATE_14400 the
'default' value of the enum by assigning it a value of 0, such that if an
endpoint fails to include the attribute, the default will be 14400.

Note that Walter Doekes included the nice comment in frame.h about why we are
purposefully assigning AST_T38_RATE_14400 a value of 0.

(closes issue ASTERISK-22275)
Reported by: Andreas Steinmetz
patches:
  fax-fix.patch uploaded by anstein (License 6523)
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Merged revisions 397256 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 397257 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@397307 f38db490-d61c-443f-a65b-d21fe96a405b