Recognize WSAEADDRINUSE in handle_connect_result.

This happens on Windows when two sockets bind to the same local port and
connect to the same remote port on a remote host. I tried this on Linux;
Linux prevents the second bind from succeeding.

http://seclists.org/nmap-dev/2012/q2/513

nsock/src/nsock_core.c

@@ -349,6 +349,7 @@ void handle_connect_result(mspool *ms, msevent *nse, enum nse_status status) {
       case EHOSTDOWN:
       case ECONNRESET:
 #ifdef WIN32
+      case WSAEADDRINUSE:
       case WSAEADDRNOTAVAIL:
 #endif
 #ifndef WIN32