A signed short was used to represent a callnumber. This is makes
it possible to attempt to access the iaxs array with a negative
index.
(closes issue #16565)
Reported by: jensvb
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@238411 65c4cc65-6c06-0410-ace0-fbb531ad65f3