Replace use of #ifndef header guards with #pragma once Modern C++, baby!
Copyright-holder and year information is extracted from git log. git history begins in 2005. So (C) from 1998..2005 is lost. Also some (C) assignment of commits where the committer didn't use --author.
mono and stereo panners. git-svn-id: svn://localhost/ardour2/branches/3.0@12577 d708f5d6-7413-0410-9779-e7cbd77b26cf