Add ancestor tracking to mempool

This implements caching of ancestor state to each mempool entry, similar to
descendant tracking, but also including caching sigops-with-ancestors (as that
metric will be helpful to future code that implements better transaction
selection in CreatenewBlock).

src/main.cpp

@@ -1323,7 +1323,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
                     FormatMoney(nModifiedFees - nConflictingFees),
                     (int)nSize - (int)nConflictingSize);
         }
-        pool.RemoveStaged(allConflicting);
+        pool.RemoveStaged(allConflicting, false);
 
         // Store transaction in memory
         pool.addUnchecked(hash, entry, setAncestors, !IsInitialBlockDownload());