[trac569] split up udpdns.[h|cc] and tcpdns.[h|cc] too

and moved them out of internal. Changed the internal/ workaround (to prevent files outside of asiolink/ to indirectly include asio.hpp), the .cc files that include the relevant headers must include asio.hpp themselves (and this is checked in the headers)
Also moved coroutine out of internal.
Tests are still todo (which is why internal/ still exists)

src/lib/asiolink/udp_socket.h

@@ -0,0 +1,48 @@
+// Copyright (C) 2011  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+#ifndef __UDP_SOCKET_H
+#define __UDP_SOCKET_H 1
+
+#ifndef ASIO_HPP
+#error "asio.hpp must be included before including this, see asiolink.h as to why"
+#endif
+
+#include <asiolink/iosocket.h>
+
+namespace asiolink {
+
+/// \brief The \c UDPSocket class is a concrete derived class of
+/// \c IOSocket that represents a UDP socket.
+///
+/// Other notes about \c TCPSocket applies to this class, too.
+class UDPSocket : public IOSocket {
+private:
+    UDPSocket(const UDPSocket& source);
+    UDPSocket& operator=(const UDPSocket& source);
+public:
+    /// \brief Constructor from an ASIO UDP socket.
+    ///
+    /// \param socket The ASIO representation of the UDP socket.
+    UDPSocket(asio::ip::udp::socket& socket) : socket_(socket) {}
+
+    virtual int getNative() const { return (socket_.native()); }
+    virtual int getProtocol() const { return (IPPROTO_UDP); }
+
+private:
+    asio::ip::udp::socket& socket_;
+};
+
+}      // namespace asiolink
+#endif // __UDP_SOCKET_H