Update copyright years.

From-SVN: r256169
diff --git a/libgcc/sync.c b/libgcc/sync.c
index ec668ed..11dcd25 100644
--- a/libgcc/sync.c
+++ b/libgcc/sync.c
@@ -1,5 +1,5 @@
 /* Out-of-line libgcc versions of __sync_* builtins.  */
-/* Copyright (C) 2008-2017 Free Software Foundation, Inc.
+/* Copyright (C) 2008-2018 Free Software Foundation, Inc.
 
 This file is part of GCC.