with ALTER TABLE ADD/REORGANIZE PARTITION
Ensure that default subpartitioning is removed when subpartitions
are defined in ADD/REORGANIZE PARTITION


mysql-test/r/partition.result:
  New test cases
mysql-test/t/partition.test:
  New test cases
sql/sql_partition.cc:
  Ensure that default subpartitioning is removed when subpartitions
  are defined in ADD/REORGANIZE PARTITION