Add a safe way to reload extensions config (don't change/delete the current...

Add a safe way to reload extensions config (don't change/delete the current extenions until extensions.conf was parsed and the new set of extensions is created) and add "extensions reload" CLI command so we could reload only extensions.conf config file without touching config files of other modules


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1183 65c4cc65-6c06-0410-ace0-fbb531ad65f3