SQL parser: Modify syntax so that the only valid top-level statement is a

procedure definition, since it's the only the one that actually works.

pars/pars0grm.y

@@ -134,9 +134,11 @@ yylex(void);
 /* Grammar follows */
 %%
 
-statement:
+top_statement:
         procedure_definition ';'
-	| stored_procedure_call
+
+statement:
+	stored_procedure_call
 	| predefined_procedure_call ';'
 	| while_statement ';'
 	| for_statement ';'