backport for bug#44059 from mysql-pe to mysql-5.1-bugteam

Using the partition with most rows instead of first partition
to estimate the cardinality of indexes.

mysql-test/r/partition.result:
  Bug#44059: Incorrect cardinality of indexes on a partitioned table
  
  Added test result
mysql-test/t/partition.test:
  Bug#44059: Incorrect cardinality of indexes on a partitioned table
  
  Added test case
sql/ha_partition.cc:
  Bug#44059: Incorrect cardinality of indexes on a partitioned table
  
  Checking which partition that has the most rows, and using that
  partition for HA_STATUS_CONST instead of first partition