Add licensing information

DrawMapCairo.cpp

@@ -1,4 +1,6 @@
 /*
+  Copyright (C) 2021 Nicole Faerber <nicole.faerber@dpin.de>
+  based on:
   DrawMap - a demo program for libosmscout
   Copyright (C) 2009  Tim Teulings
 

gmapnix.c

@@ -1,3 +1,21 @@
+/*
+ * Copyright (C) 2021 Nicole Faerber <nicole.faerber@dpin.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
 #include <stdio.h>
 #include <gtk/gtk.h>
 #include <cairo.h>