Fix or suppress MSVC level 4 warnings. Fixes #1703.

[SVN r44727]

include/boost/asio/detail/push_options.hpp

@@ -87,8 +87,10 @@
 
 # pragma warning (disable:4103)
 # pragma warning (push)
+# pragma warning (disable:4127)
 # pragma warning (disable:4244)
 # pragma warning (disable:4355)
+# pragma warning (disable:4512)
 # pragma warning (disable:4675)
 # if defined(_M_IX86) && defined(_Wp64)
 // The /Wp64 option is broken. If you want to check 64 bit portability, use a

include/boost/asio/detail/socket_ops.hpp

@@ -180,6 +180,10 @@ inline int socketpair(int af, int type, int protocol,
     socket_type sv[2], boost::system::error_code& ec)
 {
 #if defined(BOOST_WINDOWS) || defined(__CYGWIN__)
+  (void)(af);
+  (void)(type);
+  (void)(protocol);
+  (void)(sv);
   ec = boost::asio::error::operation_not_supported;
   return -1;
 #else

include/boost/asio/detail/win_iocp_socket_service.hpp

@@ -1215,8 +1215,7 @@ public:
   }
 
   // Wait until data can be received without blocking.
-  size_t receive(implementation_type& impl,
-      const null_buffers& buffers,
+  size_t receive(implementation_type& impl, const null_buffers&,
       socket_base::message_flags, boost::system::error_code& ec)
   {
     if (!is_open(impl))
@@ -1530,7 +1529,7 @@ public:
 
   // Wait until data can be received without blocking.
   size_t receive_from(implementation_type& impl,
-      const null_buffers& buffers, endpoint_type& sender_endpoint,
+      const null_buffers&, endpoint_type& sender_endpoint,
       socket_base::message_flags, boost::system::error_code& ec)
   {
     if (!is_open(impl))
@@ -1845,8 +1844,7 @@ public:
     }
 
   private:
-    static void do_completion_impl(operation* op,
-        DWORD last_error, size_t bytes_transferred)
+    static void do_completion_impl(operation* op, DWORD last_error, size_t)
     {
       // Take ownership of the operation object.
       typedef accept_operation<Socket, Handler> op_type;