Avoid cast warnings in network packet handling

See: #307

src/network/core/packet.cpp

@@ -425,7 +425,7 @@ void Packet::Recv_string(std::string &buffer, StringValidationSettings settings)
 
 	size_t length = ttd_strnlen((const char *)(this->buffer.data() + this->pos), this->Size() - this->pos - 1);
 	buffer.assign((const char *)(this->buffer.data() + this->pos), length);
-	this->pos += (uint)length + 1;
+	this->pos += (PacketSize)length + 1;
 	str_validate_inplace(buffer, settings);
 }
 

src/network/core/udp.cpp

@@ -217,7 +217,7 @@ void NetworkUDPSocketHandler::SendNetworkGameInfo(Packet *p, const NetworkGameIn
 		for (c = info->grfconfig; c != nullptr; c = c->next) {
 			if (!HasBit(c->flags, GCF_STATIC)) count++;
 		}
-		p->Send_uint8(std::min<uint>(count, NETWORK_MAX_GRF_COUNT)); // Send number of GRFs
+		p->Send_uint8(static_cast<uint8>(std::min<uint>(count, NETWORK_MAX_GRF_COUNT))); // Send number of GRFs
 
 		/* Send actual GRF Identifications */
 		uint index = 0;