Respect "AST_EDITOR" rather than "EDITOR" so as not to change the default...

Respect "AST_EDITOR" rather than "EDITOR" so as not to change the default bindings from emacs to vi (bug #2185)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@3547 65c4cc65-6c06-0410-ace0-fbb531ad65f3