Update copyright years.

From-SVN: r232055
diff --git a/libbacktrace/print.c b/libbacktrace/print.c
index 90ecaf89..74c8fcb 100644
--- a/libbacktrace/print.c
+++ b/libbacktrace/print.c
@@ -1,5 +1,5 @@
 /* print.c -- Print the current backtrace.
-   Copyright (C) 2012-2015 Free Software Foundation, Inc.
+   Copyright (C) 2012-2016 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without