Add outfuncs.c support for RawStmt nodes.

I noticed while poking at a report from Andrey Lepikhov that the
recent addition of RawStmt nodes at the top of raw parse trees
makes it impossible to print any raw parse trees whatsoever,
because outfuncs.c doesn't know RawStmt and hence fails to descend
into it.

While we generally lack outfuncs.c support for utility statements,
there is reasonably complete support for what you can find in a
raw SELECT statement.  It was not my intention to make that all
dead code ... so let's add support for RawStmt.

Back-patch to v10 where RawStmt appeared.

src/backend/nodes/outfuncs.c

@@ -15,9 +15,13 @@
  *	  have an output function defined here (as well as an input function
  *	  in readfuncs.c).  In addition, plan nodes should have input and
  *	  output functions so that they can be sent to parallel workers.
+ *
  *	  For use in debugging, we also provide output functions for nodes
- *	  that appear in raw parsetrees and path.  These nodes however need
- *	  not have input functions.
+ *	  that appear in raw parsetrees and planner Paths.  These node types
+ *	  need not have input functions.  Output support for raw parsetrees
+ *	  is somewhat incomplete, too; in particular, utility statements are
+ *	  almost entirely unsupported.  We try to support everything that can
+ *	  appear in a raw SELECT, though.
  *
  *-------------------------------------------------------------------------
  */
@@ -3347,6 +3351,20 @@ _outParamRef(StringInfo str, const ParamRef *node)
 	WRITE_LOCATION_FIELD(location);
 }
 
+/*
+ * Node types found in raw parse trees (supported for debug purposes)
+ */
+
+static void
+_outRawStmt(StringInfo str, const RawStmt *node)
+{
+	WRITE_NODE_TYPE("RAWSTMT");
+
+	WRITE_NODE_FIELD(stmt);
+	WRITE_LOCATION_FIELD(stmt_location);
+	WRITE_INT_FIELD(stmt_len);
+}
+
 static void
 _outAConst(StringInfo str, const A_Const *node)
 {
@@ -4252,6 +4270,9 @@ outNode(StringInfo str, const void *obj)
 			case T_ParamRef:
 				_outParamRef(str, obj);
 				break;
+			case T_RawStmt:
+				_outRawStmt(str, obj);
+				break;
 			case T_A_Const:
 				_outAConst(str, obj);
 				break;