Add explicit this to lambda

Implicit capture of `this` via `[=]` is deprecated in C++20 [-Wdeprecated]

src/resolver.cpp

@@ -111,7 +111,11 @@ namespace libtorrent {
 		address const ip = make_address(host, ec);
 		if (!ec)
 		{
+#if __cplusplus >= 202002L
+			m_ios.post([=, this]{ callback(h, ec, std::vector<address>{ip}); });
+#else
 			m_ios.post([=]{ callback(h, ec, std::vector<address>{ip}); });
+#endif
 			return;
 		}
 		ec.clear();
@@ -124,15 +128,23 @@ namespace libtorrent {
 				|| i->second.last_seen + m_timeout >= aux::time_now())
 			{
 				std::vector<address> ips = i->second.addresses;
+#if __cplusplus >= 202002L
+				m_ios.post([=, this] { callback(h, ec, ips); });
+#else
 				m_ios.post([=] { callback(h, ec, ips); });
+#endif
 				return;
 			}
 		}
 
 		if (flags & resolver_interface::cache_only)
 		{
 			// we did not find a cache entry, fail the lookup
+#if __cplusplus >= 202002L
+			m_ios.post([=, this] {
+#else
 			m_ios.post([=] {
+#endif
 				callback(h, boost::asio::error::host_not_found, std::vector<address>{});
 			});
 			return;

src/session_impl.cpp

@@ -5892,7 +5892,11 @@ namespace {
 		m_dht = std::make_shared<dht::dht_tracker>(
 			static_cast<dht::dht_observer*>(this)
 			, m_io_service
+#if __cplusplus >= 202002L
+			, [=, this](aux::listen_socket_handle const& sock
+#else
 			, [=](aux::listen_socket_handle const& sock
+#endif
 				, udp::endpoint const& ep
 				, span<char const> p
 				, error_code& ec

src/torrent_handle.cpp

@@ -94,7 +94,11 @@ namespace libtorrent {
 		std::shared_ptr<torrent> t = m_torrent.lock();
 		if (!t) aux::throw_ex<system_error>(errors::invalid_torrent_handle);
 		auto& ses = static_cast<session_impl&>(t->session());
-		ses.get_io_service().dispatch([=,&ses] ()
+#if __cplusplus >= 202002L
+		ses.get_io_service().dispatch([=, this, &ses] ()
+#else
+		ses.get_io_service().dispatch([=, &ses] ()
+#endif
 		{
 #ifndef BOOST_NO_EXCEPTIONS
 			try {