when replicating

The function create_virtual_tmp_table does not
set db_low_byte_first in the same way as
create_tmp_table does, causing copying from
the virtual table to a real table to get strange
values for SET types on big-endian machines.


mysql-test/extra/rpl_tests/type_conversions.test:
  Adding tests for converting between different-sized sets.
sql/sql_select.cc:
  Settng dh_low_byte_first for tables created
  with create_virtual_tmp_table.