add license header to gdbinit file

.gdbinit

@@ -1,9 +1,17 @@
+#
+# Copyright 2013-2020 Software Radio Systems Limited
+#
+# By using this file, you agree to the terms and conditions set
+# forth in the LICENSE file which can be found at the top level of
+# the distribution.
+#
 
 ############################################
 #            Pretty-Printers
 ############################################
 
 python
+
 ###### srslte::bounded_vector<T, N> ########
 
 class BoundedVectorPrinter(object):
@@ -31,4 +39,5 @@ class BoundedVectorPrinter(object):
             return BoundedVectorPrinter(val)
 
 gdb.pretty_printers.append(BoundedVectorPrinter.make)
+
 end