Editorialize a bit on new ProcessUtility() API.

Choose a saner ordering of parameters (adding a new input param after
the output params seemed a bit random), update the function's header
comment to match reality (cmon folks, is this really that hard?),
get rid of useless and sloppily-defined distinction between
PROCESS_UTILITY_SUBCOMMAND and PROCESS_UTILITY_GENERATED.

src/backend/commands/extension.c

@@ -750,10 +750,10 @@ execute_sql_string(const char *sql, const char *filename)
 			{
 				ProcessUtility(stmt,
 							   sql,
+							   PROCESS_UTILITY_QUERY,
 							   NULL,
 							   dest,
-							   NULL,
-							   PROCESS_UTILITY_QUERY);
+							   NULL);
 			}
 
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