Modify VoiceMailMain()'s a() argument to allow mailboxes to be specified by name.

(closes issue #14740)
Reported by: pj
Patches:
      issue14740_09022009.diff uploaded by seanbright (license 71)
Tested by: seanbright, lmadsen


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@221090 65c4cc65-6c06-0410-ace0-fbb531ad65f3