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/include/osmocom/core/stats.h b/include/osmocom/core/stats.h
index f50796c..e4d46ba 100644
--- a/include/osmocom/core/stats.h
+++ b/include/osmocom/core/stats.h
@@ -1,5 +1,5 @@
 /*
- * (C) 2015 by Sysmocom s.f.m.c. GmbH
+ * (C) 2015 by sysmocom - s.f.m.c. GmbH
  *
  * All Rights Reserved
  *