code: function incPnodeVersion (pnode) {
          pnode._version = pnode._version ? pnode._version + 1 : 1
          pnode._mtxid = ptree.txid
          pnode._mtime = new Date
          if (!pnode._ctxid) pnode._ctxid = pnode._mtxid
          if (!pnode._ctime) pnode._ctime = pnode._mtime
          return pnode
      }
docs: increment pnode version