Changed variable name for improved clarity and debugging possibilities
Fixed bug in not assigning subpart_type


mysql-test/t/partition.test:
  Added new test case
sql/partition_info.cc:
  Changed variable name for improved clarity and debugging possibilities
  Fixed bug in not assigning subpart_type
sql/sql_partition.cc:
  Changed variable name for improved clarity and debugging possibilities
  Fixed bug in not assigning subpart_type