FEATURE Add NETCONF time function

Add implementation of public functions to work with timestamps in the
NETCONF format.
diff --git a/src/config.h b/src/config.h
new file mode 100644
index 0000000..45f0cc8
--- /dev/null
+++ b/src/config.h
@@ -0,0 +1,31 @@
+/**
+ * \file config.h
+ * \author Radek Krejci <rkrejci@cesnet.cz>
+ * \brief libnetconf2 various configuration settings.
+ *
+ * Copyright (c) 2015 CESNET, z.s.p.o.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of the Company nor the names of its contributors
+ *    may be used to endorse or promote products derived from this
+ *    software without specific prior written permission.
+ *
+ */
+
+#ifndef NC_CONFIG_H_
+#define NC_CONFIG_H_
+
+/*
+ * Mark all objects as hidden and export only objects explicitly marked to be part of the public API.
+ */
+#define API __attribute__((visibility("default")))
+
+#endif /* NC_CONFIG_H_ */