make 'core show settings' should show all settable directories

(closes issue #17086)
Reported by: tzafrir
Patches:
      asterisk_extra_settings_dirs.diff uploaded by tzafrir (license 46)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@254162 65c4cc65-6c06-0410-ace0-fbb531ad65f3