ndb/include/debugger/EventLogger.hpp:
  add definition for new printLogEvent() function in CommandInterpreter.cpp
ndb/src/mgmclient/CommandInterpreter.cpp:
  add a printLogEvent() function to print log event;
  filter "<PING>" by ndb_logevent_get_next() in event_thread_run();
  filter "<PING>" by ndb_logevent_get_next() in executeStartBackup();
  and make executeStartBackup() same in both 5.0 and 5.1
ndb/src/mgmclient/Makefile.am:
  add link to use ndb_logevent_get_next()
mysql-test/r/ndb_backup_print.result:
  testcase result for ndb_backup_print
  produced by mysql_test_run.pl
mysql-test/t/ndb_backup_print.test:
  add testcase for ndb_mgm -e "start backup", check outupt format