CREDITS clean up

As discussed online http://lists.digium.com/pipermail/asterisk-dev/2012-October/057245.html the credits file needs some cleaning.  This is 95% whitespace with a few additions found in file headers.  Further additions should be added here instead of in the file being updated.

(issue ASTERISK-20259)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374887 65c4cc65-6c06-0410-ace0-fbb531ad65f3