Handle AT_ReAddComment in test_ddl_deparse, and add a catch-all default.

In the passing, also move AT_ReAddComment to more logical position in the
enum, after all the Constraint-related subcommands.

This fixes a compiler warning, added by commit e42375fc. Backpatch to 9.5,
like that patch.

src/include/nodes/parsenodes.h

@@ -1474,7 +1474,6 @@ typedef enum AlterTableType
 	AT_AddConstraint,			/* add constraint */
 	AT_AddConstraintRecurse,	/* internal to commands/tablecmds.c */
 	AT_ReAddConstraint,			/* internal to commands/tablecmds.c */
-	AT_ReAddComment,			/* internal to commands/tablecmds.c */
 	AT_AlterConstraint,			/* alter constraint */
 	AT_ValidateConstraint,		/* validate constraint */
 	AT_ValidateConstraintRecurse,		/* internal to commands/tablecmds.c */
@@ -1483,6 +1482,7 @@ typedef enum AlterTableType
 	AT_AddIndexConstraint,		/* add constraint using existing index */
 	AT_DropConstraint,			/* drop constraint */
 	AT_DropConstraintRecurse,	/* internal to commands/tablecmds.c */
+	AT_ReAddComment,			/* internal to commands/tablecmds.c */
 	AT_AlterColumnType,			/* alter column type */
 	AT_AlterColumnGenericOptions,		/* alter column OPTIONS (...) */
 	AT_ChangeOwner,				/* change owner */

src/test/modules/test_ddl_deparse/test_ddl_deparse.c

@@ -151,6 +151,9 @@ get_altertable_subcmdtypes(PG_FUNCTION_ARGS)
 			case AT_DropConstraintRecurse:
 				strtype = "DROP CONSTRAINT (and recurse)";
 				break;
+			case AT_ReAddComment:
+				strtype = "(re) ADD COMMENT";
+				break;
 			case AT_AlterColumnType:
 				strtype = "ALTER COLUMN SET TYPE";
 				break;
@@ -253,6 +256,8 @@ get_altertable_subcmdtypes(PG_FUNCTION_ARGS)
 			case AT_GenericOptions:
 				strtype = "SET OPTIONS";
 				break;
+			default:
+				strtype = "unrecognized";
 		}
 
 		astate =