This will hopefully avoiid annoying crashes when running with --debug
Fix warnings  from the above in mysqltest.c


client/mysqltest.c:
  Fix format specifier warnings in mysqltest.c
include/my_dbug.h:
  Add ATTRIBUTE_FORMAT specifier to _db_doprnt, which is used by DBUG_PRINT
  This will hopefully avoiid annoying crashes when running with --debug