Add a SECURITY LABEL command.

This is intended as infrastructure to support integration with label-based
mandatory access control systems such as SE-Linux. Further changes (mostly
hooks) will be needed, but this is a big chunk of it.

KaiGai Kohei and Robert Haas

src/include/nodes/parsenodes.h

@@ -1850,6 +1850,20 @@ typedef struct CommentStmt
 	char	   *comment;		/* Comment to insert, or NULL to remove */
 } CommentStmt;
 
+/* ----------------------
+ *				SECURITY LABEL Statement
+ * ----------------------
+ */
+typedef struct SecLabelStmt
+{
+	NodeTag		type;
+	ObjectType	objtype;		/* Object's type */
+	List	   *objname;		/* Qualified name of the object */
+	List	   *objargs;		/* Arguments if needed (eg, for functions) */
+	char	   *provider;		/* Label provider (or NULL) */
+	char	   *label;			/* New security label to be assigned */
+} SecLabelStmt;
+
 /* ----------------------
  *		Declare Cursor Statement
  *