move devices from hints into an ao2_container

by splitting up devices from hints into an own ao2_container the callback to
get these devices for statechange handling is faster.
with this changes the length of a device used in a hint isnt longer restricted
to 80 characters.

Tests showed that calling handle_statechange is 40 times faster if no hints
are used and 25 times faster if there are any hints.

(closes issue #17928)
Reported by: mdu113
Tested by: schmidts

Review: https://reviewboard.asterisk.org/r/1003/



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@296752 65c4cc65-6c06-0410-ace0-fbb531ad65f3