Updated PXE UDP implementation to use the new Etherboot UDP API.

Updated PXE API dispatcher to use copy_{to,from}_user, and moved to
arch/i386 since the implementation is quite architecture-dependent.
(The individual PXE API calls can be largely
architecture-independent.)

src/net/udp.c

@@ -66,6 +66,18 @@ void udp_connect ( struct udp_connection *conn, struct sockaddr_tcpip *peer ) {
 	memcpy ( &conn->peer, peer, sizeof ( conn->peer ) );
 }
 
+/**
+ * Connect UDP connection to all remote hosts and ports
+ *
+ * @v conn		UDP connection
+ *
+ * This undoes the effect of a call to udp_connect(), i.e. allows the
+ * connection to receive packets from all remote hosts and ports.
+ */
+void udp_connect_promisc ( struct udp_connection *conn ) {
+	memset ( &conn->peer, 0, sizeof ( conn->peer ) );
+}
+
 /**
  * Open a local port
  *