Changed the management of the wireless interfaces, from creation to usage.

The virtual interfaces are created at the startup of the wtp to reduce the time
required to configure a wireless interface.
Applied some patches to build the WTP on OpenWRT trunk

src/wtp/wtp_dfa_run.c

@@ -2,6 +2,7 @@
 #include "capwap_dfa.h"
 #include "capwap_element.h"
 #include "wtp_dfa.h"
+#include "wtp_radio.h"
 
 /* */
 static int send_echo_request() {