examples: Add simple storage implementation using GVariant

This is useful so that the enroll and verify examples will not use the
deprecated API anymore.

examples/storage.h

@@ -0,0 +1,27 @@
+/*
+ * Trivial storage driver for example programs
+ *
+ * Copyright (C) 2019 Benjamin Berg <bberg@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef __STORAGE_H
+#define __STORAGE_H
+
+int print_data_save(struct fp_print_data *fp_data, enum fp_finger finger);
+struct fp_print_data* print_data_load(struct fp_dev *dev, enum fp_finger finger);
+
+#endif /* __STORAGE_H */