Make chan_local module references tied to local_pvt lifetime.

Make chan_local module references tied to local_pvt lifetime.

The chan_local module references were manually tied to the existence of
the ;1 and ;2 channel links.

* Made chan_local module references tied to the existence of the local_pvt
structure as well as automatically take care of the module references.

* Tweaked the wording of the local_fixup() failure warning message to make
sense.

Review: https://reviewboard.asterisk.org/r/2181/
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Merged revisions 378088 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 378089 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@378090 65c4cc65-6c06-0410-ace0-fbb531ad65f3