Backport state interface changes to app_queue from trunk.

Backport state interface changes to app_queue from trunk.

After several issues raised on the Asterisk bugtracker against
the 1.4 branch were determined to be fixable with the state interface
change available in the 1.6.X series, it finally came time to just
suck it up and backport the change.

For a detailed explanation of what this change entails, the original
trunk commit for this feature may be found here:

http://svn.digium.com/view/asterisk?view=revision&revision=97203

In addition, the details for the use of this change to fix the problems
stated in issue #12970 may be found in the review request I made for
this change. It is linked below.

(closes issue #12970)
Reported by: edugs15

Review: http://reviewboard.digium.com/r/116

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@184980 65c4cc65-6c06-0410-ace0-fbb531ad65f3