Make partitioned tables report the row format of the underlying
  tables (when they are all the same).


mysql-test/r/partition.result:
  Add new results
mysql-test/t/partition.test:
  Add regression test
sql/ha_partition.cc:
  Add get_row_type(), which peeks at the underlying tables and returns
  the row_type if they are consistent.
sql/ha_partition.h:
  Add get_row_type() method