Small improvements to fuzzer for NetHackW.

Can toggle fuzzer on/off using "Pause" key if attached to debugger.
Extended command selected randomly.

win/win32/mhdlg.c

@@ -167,6 +167,15 @@ INT_PTR CALLBACK ExtCmdDlgProc(HWND, UINT, WPARAM, LPARAM);
 int
 mswin_ext_cmd_window(int *selection)
 {
+    if (iflags.debug_fuzzer) {
+        *selection = rn2(extcmdlist_length + 1) - 1;
+
+        if (*selection != -1)
+            return IDOK;
+        else
+            return IDCANCEL;
+    }
+
     INT_PTR ret;
     struct extcmd_data data;