[OPTIM] more cache-friendly struct eb_node
[OPTIM] more cache-friendly struct eb_node

Moving the dups at the end of the first cacheline shows
better access patterns. Dups are very rare and only slightly
impacted by this change. Other inserts and walks are now faster.

sociomantic-tsunami/ebtree,sociomantic-tsunami/ebtree,haproxy/ebtree