Fix/Update copyright notices; Add SPDX annotation

Let's fix some erroneous/accidential references to wrong license,
update copyright information where applicable and introduce a
SPDX-License-Identifier to all files.

Change-Id: I39af26c6aaaf5c926966391f6565fc5936be21af
diff --git a/src/prim.c b/src/prim.c
index d18dbd7..3c8a7f1 100644
--- a/src/prim.c
+++ b/src/prim.c
@@ -1,4 +1,10 @@
-/*! \addtogroup prim
+/*! 
+ * (C) 2015-2017 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * \addtogroup prim
  *  @{
  *  \file prim.c */