This patch allows an event mask to be sent on a manager login session

This patch allows an event mask to be sent on a manager login session
either using an integer value or a ',' sep list of flags exactly like
the manager.conf read and write lines.

e.g.
Events: system,call,log
or
Events: off
or
Events: on

Also you can change it mid-session with Action: Events

e.g.
Action: Events
EventMask: system,call,log

-Tony (anthm)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@3399 65c4cc65-6c06-0410-ace0-fbb531ad65f3