This text was already in the About dialog, but should be here too.
Verbatim copy of https://www.gnu.org/licenses/gpl-2.0.txt Also remove the "How to apply" section below "End of Terms", this allows to use this file 1:1 as License in Installer.
git-svn-id: svn://localhost/trunk/ardour2@4 d708f5d6-7413-0410-9779-e7cbd77b26cf
