stcp: ed25519 pubkey exchange in handshake, fix instance destroy segfault, fix chat_tcp_test

- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll
- stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close
- utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP),
  add deferred drain in both Phase J and L
- stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39,
  exchange ed25519_pubkey in both handshake directions
- etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in
  etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb
- chat_sync.c: fix lk->conn NULL dereference for TCP links
- test_stcp.c: update stcp_server_create/stcp_client_connect callsites
- tools/chat_tcp_test: change transport udp→tcp

tools/chatgui/zxing-cpp/core/src/BitArray.cpp

@@ -0,0 +1,38 @@
+/*
+* Copyright 2016 Nu-book Inc.
+* Copyright 2016 ZXing authors
+*/
+// SPDX-License-Identifier: Apache-2.0
+
+#include "BitArray.h"
+
+#include "ByteArray.h"
+
+#include <cstddef>
+#include <stdexcept>
+
+namespace ZXing {
+
+void
+BitArray::bitwiseXOR(const BitArray& other)
+{
+	if (size() != other.size()) {
+		throw std::invalid_argument("BitArray::xor(): Sizes don't match");
+	}
+	for (size_t i = 0; i < _bits.size(); i++) {
+		// The last int could be incomplete (i.e. not have 32 bits in
+		// it) but there is no problem since 0 XOR 0 == 0.
+		_bits[i] ^= other._bits[i];
+	}
+}
+
+ByteArray BitArray::toBytes(int bitOffset, int numBytes) const
+{
+	ByteArray res(numBytes == -1 ? (size() - bitOffset + 7) / 8 : numBytes);
+	for (int i = 0; i < Size(res); i++)
+		for (int j = 0; j < 8; j++)
+			AppendBit(res[i], (numBytes != -1 || bitOffset < size()) ? get(bitOffset++) : false);
+	return res;
+}
+
+} // ZXing