The contents of command.c, creatinh.c, define.c, remove.c and rename.c

have been divided according to the type of object manipulated - so ALTER
TABLE code is in tablecmds.c, aggregate commands in aggregatecmds.c and
so on.

A few common support routines remain in define.c (prototypes in
src/include/commands/defrem.h).

No code has been changed except for includes to reflect the new files.
The prototypes for aggregatecmds.c, functioncmds.c, operatorcmds.c,
and typecmds.c remain in src/include/commands/defrem.h.

From John Gray <jgray@azuli.co.uk>

src/include/commands/tablecmds.h

@@ -0,0 +1,63 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablecmds.h
+ *	  prototypes for tablecmds.c.
+ *
+ *
+ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $Id: tablecmds.h,v 1.1 2002/04/15 05:22:04 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef TABLECMDS_H
+#define TABLECMDS_H
+
+#include "nodes/parsenodes.h"
+
+extern void AlterTableAddColumn(Oid myrelid, bool inherits,
+								ColumnDef *colDef);
+
+extern void AlterTableAlterColumnDefault(Oid myrelid, bool inh,
+										 const char *colName,
+										 Node *newDefault);
+
+extern void AlterTableAlterColumnDropNotNull(Oid myrelid, bool inh,
+											 const char *colName);
+
+extern void AlterTableAlterColumnSetNotNull(Oid myrelid, bool inh,
+											const char *colName);
+
+extern void AlterTableAlterColumnFlags(Oid myrelid, bool inh,
+									   const char *colName,
+									   Node *flagValue, const char *flagType);
+
+extern void AlterTableDropColumn(Oid myrelid, bool inh,
+					 			 const char *colName, int behavior);
+
+extern void AlterTableAddConstraint(Oid myrelid, bool inh,
+									List *newConstraints);
+
+extern void AlterTableDropConstraint(Oid myrelid, bool inh,
+									 const char *constrName, int behavior);
+
+extern void AlterTableCreateToastTable(Oid relOid, bool silent);
+
+extern void AlterTableOwner(Oid relationOid, int32 newOwnerSysId);
+
+extern Oid	DefineRelation(CreateStmt *stmt, char relkind);
+
+extern void RemoveRelation(const RangeVar *relation);
+
+extern void TruncateRelation(const RangeVar *relation);
+
+extern void renameatt(Oid relid,
+		  const char *oldattname,
+		  const char *newattname,
+		  bool recurse);
+
+extern void renamerel(Oid relid,
+		  const char *newrelname);
+
+#endif   /* TABLECMDS_H */