Fix Plink, the serial backend, and local-proxy support on Win98SE (at least),

which have been broken since r6797.
(At least some versions of Win9x are gratuitously picky about the arguments to
CreateThread(), requiring lpThreadId not to be NULL.)

[originally from svn r7132]
[r6797 == 291533d3f9]

windows/winhandl.c

@@ -332,6 +332,7 @@ struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
 				void *privdata, int flags)
 {
     struct handle *h = snew(struct handle);
+    DWORD in_threadid; /* required for Win9x */
 
     h->output = FALSE;
     h->u.i.h = handle;
@@ -349,7 +350,7 @@ struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
     add234(handles_by_evtomain, h);
 
     CreateThread(NULL, 0, handle_input_threadfunc,
-		 &h->u.i, 0, NULL);
+		 &h->u.i, 0, &in_threadid);
     h->u.i.busy = TRUE;
 
     return h;
@@ -359,6 +360,7 @@ struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
 				 void *privdata, int flags)
 {
     struct handle *h = snew(struct handle);
+    DWORD out_threadid; /* required for Win9x */
 
     h->output = TRUE;
     h->u.o.h = handle;
@@ -378,7 +380,7 @@ struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
     add234(handles_by_evtomain, h);
 
     CreateThread(NULL, 0, handle_output_threadfunc,
-		 &h->u.i, 0, NULL);
+		 &h->u.i, 0, &out_threadid);
 
     return h;
 }