query
Problem:
There was a wrong context assigned to the columns that were added in insert_fields()
when expanding a '*'. When this is done in a prepared statement it causes 
fix_fields() to fail to find the table that these columns reference.
Actually the right context is set in setup_natural_join_row_types() called at the 
end of setup_tables(). However when executed in a context of a prepared statement
setup_tables() resets the context, but setup_natural_join_row_types() was not
setting it to the correct value assuming it has already done so.

Solution:
The top-most, left-most NATURAL/USING join must be set as a 
first_name_resolution_table in context even when operating on prepared statements.


mysql-test/r/join.result:
  testsuite for the bug
mysql-test/t/join.test:
  testsuite for the bug
sql/sql_base.cc:
  The context must be set even when executed as prepared statement.