(Needed to check if memory allocated with mysql_once_init() has been freed)



include/my_sys.h:
  Added possibility to detect if libmysqld is restarted
mysys/my_init.c:
  Added possibility to detect if libmysqld is restarted
sql/handler.cc:
  Detect if libmysqld is restarted
  Simple optimization of ha_known_exts()