containers: add magic container infrastructure

Add support for dynamic containers, with enough flexibility to also
replace our existing container ID replacement functionality.

containers.h

@@ -0,0 +1,36 @@
+/* MiniDLNA media server
+ * Copyright (C) 2014  NETGEAR
+ *
+ * This file is part of MiniDLNA.
+ *
+ * MiniDLNA is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * MiniDLNA 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with MiniDLNA. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+struct magic_container_s {
+	const char *name;
+	const char *objectid_match;
+	const char **objectid;
+	const char *objectid_sql;
+	const char *parentid_sql;
+	const char *refid_sql;
+	const char *child_count;
+	const char *where;
+	const char *orderby;
+	int max_count;
+	int required_flags;
+};
+
+extern struct magic_container_s magic_containers[];
+
+struct magic_container_s *in_magic_container(const char *id, int flags, const char **real_id);
+struct magic_container_s *check_magic_container(const char *id, int flags);