Table functions: make name resolution see the return_table.

This is a part of dj's GSoC project. not anymore
When MDEV-8343 is done, we will be able to parse stored function declarations, like:

CREATE FUNCTION ... RETURNS TABLE ret_table (...)  BEGIN

  insert into ret_table values (1);

END;

but an attempt to check the stored function will fail with "Unknown table ret_table" error.

This task is about fixing the process of name resolution for statements inside stored functions to know there is a returned table ret_table.