[#3388] Fix licencing issue in gnome client sources

sflphone-client-gnome/src/accountlist.h

sflphone-client-gnome/src/actions.h

sflphone-client-gnome/src/callable_obj.h

sflphone-client-gnome/src/codeclist.h

sflphone-client-gnome/src/conference_obj.h

sflphone-client-gnome/src/config/accountconfigdialog.h

sflphone-client-gnome/src/config/accountlistconfigdialog.h

sflphone-client-gnome/src/config/addressbook-config.h

sflphone-client-gnome/src/config/assistant.h

sflphone-client-gnome/src/config/audioconf.h

sflphone-client-gnome/src/config/hooks-config.h

sflphone-client-gnome/src/config/preferencesdialog.h

sflphone-client-gnome/src/config/shortcuts-config.h

sflphone-client-gnome/src/config/tlsadvanceddialog.h

sflphone-client-gnome/src/config/utils.h

sflphone-client-gnome/src/config/zrtpadvanceddialog.h

sflphone-client-gnome/src/contacts/addressbook.h

sflphone-client-gnome/src/contacts/addressbook/eds.h

sflphone-client-gnome/src/contacts/calllist.h

sflphone-client-gnome/src/contacts/calltab.h