cdr_radius, cel_radius: build agains libfreeradius-client

Asterisk's RADIUS module currently build against libradiusclient-ng, but this
project has been superseeded by libfreeradius-client. The API is 99% compatible
except that the header name has changed, the library name has changed, and
the configuration file location has changed.

(closes issue ASTERISK-22980)
Reported by: Jeremy Lainé
Patches:
     freeradius-client.patch uploaded by sharky (license 6561)
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Merged revisions 406801 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 406802 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@406803 f38db490-d61c-443f-a65b-d21fe96a405b
res_pjsip_pubsub: potential crash on timeout

What seems to be happening is if a subscription has been terminated and the
subscription timeout/expires is less than the time it takes for all pending
transactions (currently on the subscription) to end then the subscription
timer will not have been canceled yet and sub will be null.  Since the
subscription has already been canceled nothing needs to be done so a null
check in the asterisk code is sufficient in working around this problem.

(closes issue ASTERISK-23129)
Reported by: Dan Jenkins


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@406847 f38db490-d61c-443f-a65b-d21fe96a405b