Added missing mutex_unlock to slave replication code.


include/my_sys.h:
  removed init_count from IO_CACHE.
  General cleanup.
innobase/srv/srv0srv.c:
  Initailize slots to avoid purify warnings.
  Removed some compiler warnings.
mysql-test/mysql-test-run.sh:
  Automatic start of slave under gdb
mysys/mf_iocache.c:
  removed init_count
sql/field.cc:
  Cleanup
sql/log.cc:
  Cleanup
  added open_count variable.
sql/log_event.cc:
  cleanup
  use is_prefix instead of memcmp()
sql/repl_failsafe.cc:
  cleanup
sql/slave.cc:
  cleanup
  use MYSQL_LOG->open_count instead of IO_CACHE->init_count
  Added missing mutex_unlock()
sql/slave.h:
  cleanup
sql/sql_class.h:
  cleanup
  Added open_count to MYSQL_LOGL
sql/sql_parse.cc:
  removed compiler warning
sql/sql_repl.cc:
  added DBUG_xxx
sql/unireg.h:
  Added BIN_LOG_HEADER_SIZE