Copyedit the license's revised text: (1) remove unnecessary repitition use of the word 'license' from the top of the header and source files (2) add the standard 'we hope it's useful, but no warranty' clause to COPYING (3) make explicit that linking OpenSSL is allowed (see https://people.gnome.org/~markmc/openssl-and-the-gpl.html for background) (4) sync the Qt and GTK+ clients' license popups with COPYING's revised text

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14241 f4695dd4-2c0a-0410-b89c-da849a56a58e