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/common/capwap_debug.h

@@ -19,7 +19,11 @@ void capwap_free_debug(void* p, const char* file, const int line);
 int capwap_check_memory_leak(int verbose);
 void capwap_dump_memory(void);
 
+#ifdef USE_DEBUG_BACKTRACE
 void capwap_backtrace_callstack(void);
+#else
+#define capwap_backtrace_callstack()	(0)
+#endif
 
 #else