C4::Items uses a single subroutine from C4::Reserves, CheckReserves(), in a single on of it's subroutines, GetItemsInfo().  The only data exported is in the field "count_reserves" which gives the reserve status.  This in turn is only used  in opac/opac-detail.pl to display "on hold" in the holdings table if the item is currently waiting on the holds shelf to be picked up.  There are no other uses of this information.

We can remove CheckReserves() from GetItemsInfo(), and add a different call in opac/opac-details.pl to get whether the particular item is on hold or not.  This will remove a circular dependency, likely speeding up the overall code (as we won't need to load all of C4::Reserves every time we load C4::Items).