When fields are inserted instead of * in the select list they were not marked
for check for the ONLY_FULL_GROUP_BY mode.

The Field_iterator_table::create_item() function now marks newly created
items for check when in the ONLY_FULL_GROUP_BY mode.
The setup_wild() and the insert_fields() functions now maintain the
cur_pos_in_select_list counter for the ONLY_FULL_GROUP_BY mode.