Add audio announcement option to app_page

As described in the CHANGES file:
* MeetMe has a new option 'G' to play an announcement before joining a
  conference.
* Page has a new option 'A(x)' which will playback an announcement 
  simultaneously to all paged phones (and optionally excluding the caller's one 
  using the new option 'n') before the call is bridged.

To add the new option to meetme, the conference flag options had to be extended 
to 64 bits.

(closes issue #14365)
Reported by: dferrer
Patches:
      page_announce.patch uploaded by dferrer (license 525)
      modified by me

Review: https://reviewboard.asterisk.org/r/188/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@234173 65c4cc65-6c06-0410-ace0-fbb531ad65f3