First entry! Tell people about the callerid changes with manager.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@44262 65c4cc65-6c06-0410-ace0-fbb531ad65f3

UPGRADE.txt

 Information for Upgrading From Previous Asterisk Releases
 =========================================================
 
+Manager:
+
+* The CallerID fields across manager events have now been made more
+  consistent. CallerID Number will be sent as CallerIDNum and CallerID
+  Name will be sent as CallerIDName wherever used.