- added bdb-cache-parts
- modified bdb-cache-size to support more than 4G
- added bdb-region-size (size of memory pool for storing file names used in transaction)


sql/ha_berkeley.cc:
  - added bdb-cache-parts
  - modified bdb-cache-size to support more than 4G
  - added bdb-region-size (size of memory pool for storing file names used in transaction)
sql/ha_berkeley.h:
  - added bdb-cache-parts
  - modified bdb-cache-size to support more than 4G
  - added bdb-region-size (size of memory pool for storing file names used in transaction)
sql/mysqld.cc:
  - added bdb-cache-parts
  - modified bdb-cache-size to support more than 4G
  - added bdb-region-size (size of memory pool for storing file names used in transaction)
sql/set_var.cc:
  - added bdb-cache-parts
  - modified bdb-cache-size to support more than 4G
  - added bdb-region-size (size of memory pool for storing file names used in transaction)