Added two status variables: 
  binlog_cache_use - counts number of transactions that used somehow
    transaction temporary binary log.
  binlog_cache_disk_use - counts number of transactions that required
    disk I/O for storing info in this this binary log.


include/my_sys.h:
  Added disk_writes member to the IO_CACHE structure for counting number
  of times when IO_CACHE was forced to write to disk.
mysql-test/r/rpl_relayrotate.result:
  Fixed test result since added test for binlog_cache_use and 
  binlog_cache_disk_use status variables.
mysql-test/t/rpl_relayrotate.test:
  Added test for binlog_cache_use and binlog_cache_disk_use status 
  variables.
  Now dropping t1 table on master too.
mysys/mf_iocache.c:
  Added disk_writes member to the IO_CACHE structure for counting number
  of times when IO_CACHE was forced to write to disk.
sql/handler.cc:
  Added support for binlog_cache_use and binlog_cache_disk_use status
  variable. First one is incremented if transaction used somehow 
  transaction temporary binary log (doesn't matter in memory only or 
  with writes to disk), the second one is incremented if this binary 
  log was flushed to disk at some point.
sql/mysql_priv.h:
  Added declaration of status variables binlog_cache_use and 
  binlog_cache_disk_use.
sql/mysqld.cc:
  Added status variables binlog_cache_use and binlog_cache_disk_use.
BitKeeper/etc/logging_ok:
  Logging to logging@openlogging.org accepted