Logical replication

- Add PUBLICATION catalogs and DDL
- Add SUBSCRIPTION catalog and DDL
- Define logical replication protocol and output plugin
- Add logical replication workers

From: Petr Jelinek <petr@2ndquadrant.com>
Reviewed-by: Steve Singer <steve@ssinger.info>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Erik Rijkers <er@xs4all.nl>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

src/include/replication/pgoutput.h

@@ -0,0 +1,29 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgoutput.h
+ *		Logical Replication output plugin
+ *
+ * Copyright (c) 2015, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		pgoutput.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PGOUTPUT_H
+#define PGOUTPUT_H
+
+
+typedef struct PGOutputData
+{
+	MemoryContext	context;			/* private memory context for transient
+										 * allocations */
+
+	/* client info */
+	uint32			protocol_version;
+
+	List		   *publication_names;
+	List		   *publications;
+} PGOutputData;
+
+#endif /* PGOUTPUT_H */