Fix compiler warnings emitted when compiling under stock OpenBSD 6.3

src/txmempool.cpp

@@ -693,18 +693,18 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
         // Check children against mapNextTx
         CTxMemPool::setEntries setChildrenCheck;
         auto iter = mapNextTx.lower_bound(COutPoint(it->GetTx().GetHash(), 0));
-        int64_t childSizes = 0;
+        uint64_t child_sizes = 0;
         for (; iter != mapNextTx.end() && iter->first->hash == it->GetTx().GetHash(); ++iter) {
             txiter childit = mapTx.find(iter->second->GetHash());
             assert(childit != mapTx.end()); // mapNextTx points to in-mempool transactions
             if (setChildrenCheck.insert(childit).second) {
-                childSizes += childit->GetTxSize();
+                child_sizes += childit->GetTxSize();
             }
         }
         assert(setChildrenCheck == GetMemPoolChildren(it));
         // Also check to make sure size is greater than sum with immediate children.
         // just a sanity check, not definitive that this calc is correct...
-        assert(it->GetSizeWithDescendants() >= childSizes + it->GetTxSize());
+        assert(it->GetSizeWithDescendants() >= child_sizes + it->GetTxSize());
 
         if (fDependsWait)
             waitingOnDependants.push_back(&(*it));