This is a regression from the fix of bug#14740889.
The fix started using another set of expressions as the source for
the temporary table used for the materialized cursor. However,
JOIN::make_tmp_tables_info() calls setup_copy_fields() which creates
an Item_copy wrapper object on top of the function being selected.

The Item_copy objects were not properly handled by create_tmp_table -
they were simply ignored. This patch creates temporary table fields
based on the underlying item of the Item_copy objects.

sql/sql_tmp_table.cc
  In create_tmp_table(), create temporary table fields based on
  Item_copy's underlying item.