Item_extract needs special implementation for eq().
Item_func::eq doesn't work correctly because we have to compare 
Item_extract::int_type parameters also

We need to propagate this to 4.1


sql/item_timefunc.cc:
  Item_extract::eq implementation added
sql/item_timefunc.h:
  Item_extract::eq definition added
BitKeeper/etc/logging_ok:
  Logging to logging@openlogging.org accepted