fix VS2010 build warning

libs/sofia-sip/libsofia-sip-ua/tport/ws.c

 #include "ws.h"
 #include <pthread.h>
 
+#ifdef _MSC_VER
+/* warning C4706: assignment within conditional expression*/
+#pragma warning(disable: 4706)
+#endif
+
 #ifndef _MSC_VER
 #include <fcntl.h>
 #endif