[Freeciv-Dev] (PR#2960) Correction for old tile system

["Eric S. Raymond via RT" <rt@xxxxxxxxxxxxxx>]

Note to potential committers evaluating this patch: if you test on a
build that uses the old tile system, remove the call yo
delete_hash_entry() that it uses.  Otherwise it's just possible 
you might get a double-free error on a duplicated tag.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>

If we believe absurdities, we shall commit atrocities.
                -- Voltaire