added default constructor to session_proxy

docs/manual.html

@@ -327,7 +327,12 @@ destruction of the session is performed from the <tt class="docutils literal"><s
 on it (since the session is being closed down, no operations are allowed on it). The
 only valid operation is calling the destructor:</p>
 <pre class="literal-block">
-class session_proxy { ~session_proxy() };
+class session_proxy
+{
+public:
+        session_proxy();
+        ~session_proxy()
+};
 </pre>
 </div>
 <div class="section" id="add-torrent">

docs/manual.rst

@@ -175,7 +175,12 @@ destruction of the session is performed from the ``session`` destructor call unt
 on it (since the session is being closed down, no operations are allowed on it). The
 only valid operation is calling the destructor::
 
-	class session_proxy { ~session_proxy() };
+	class session_proxy
+	{
+	public:
+		session_proxy();
+		~session_proxy()
+	};
 
 
 add_torrent()