Remove unused and obsolete classes and tidy up:

Many classes required to support type-erasure of handlers and boost::asio
types are now obsolete, so these classes and files are removed:
HTTPClientType, FixedInputBuffer, PeerRole, socket_wrapper,
client_session, basic_url, abstract_socket, buffer_sequence, memory_buffer,
enable_wait_for_async, shared_handler, wrap_handler, streambuf,
ContentBodyBuffer, SSLContext, completion-handler based handshake detectors.
These structural changes are made:
* Some missing includes added to headers
* asio module directory flattened

beast/module/asio/HTTPMessage.cpp

@@ -0,0 +1,56 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of Beast: https://github.com/vinniefalco/Beast
+    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
+
+    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 THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
+*/
+//==============================================================================
+
+#include <beast/module/asio/HTTPMessage.h>
+
+namespace beast {
+
+HTTPMessage::HTTPMessage (HTTPVersion const& version_,
+                          StringPairArray& fields,
+                          DynamicBuffer& body)
+    : m_version (version_)
+    , m_headers (fields)
+{
+    m_body.swapWith (body);
+}
+
+HTTPVersion const& HTTPMessage::version () const
+{
+    return m_version;
+}
+
+HTTPHeaders const& HTTPMessage::headers () const
+{
+    return m_headers;
+}
+
+DynamicBuffer const& HTTPMessage::body () const
+{
+    return m_body;
+}
+
+String HTTPMessage::toString () const
+{
+    String s;
+    s << "HTTP " << version().toString() << newLine;
+    s << m_headers.toString ();
+    return s;
+}
+
+}