bug in integration SQL parser to plpgsq

Hello

it doesn't support EXPLAIN as possible begin of SQL statement:

postgres=# create or replace function foo(_a int) returns void as
$$declare s varchar; begin for s in explain select * from omega where
a = _a loop raise notice '%', s; end loop; return; end; $$ language
plpgsql;
CREATE FUNCTION
postgres=# select foo(10);
ERROR:  column "_a" does not exist
CONTEXT:  PL/pgSQL function "foo" line 1 at FOR over SELECT rows

postgres=# create or replace function foo(_a int) returns void as
$$declare s varchar; begin for s in select * from omega where a = _a
loop raise notice '%', s; end loop; return; end; $$ language plpgsql;
CREATE FUNCTION
postgres=# select foo(10);foo
-----

(1 row)

Regards
Pavel Stehule