patch 9.0.0802: MS-Windows: cannot map console mouse scroll events

Problem:    MS-Windows: cannot map console mouse scroll events.
Solution:   Change CSI to K_SPECIAL when checking for a mapping. (Christopher
            Plewright, closes #11410)
diff --git a/src/os_win32.c b/src/os_win32.c
index 03b3ac0..ca1799f 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -1265,7 +1265,7 @@
 #ifdef FEAT_PROP_POPUP
     int lcol = g_xMouse;
     int lrow = g_yMouse;
-    wp = mouse_find_win(&lrow, &lcol, FAIL_POPUP);
+    wp = mouse_find_win(&lrow, &lcol, FIND_POPUP);
     if (wp != NULL && popup_is_popup(wp))
     {
 	g_nMouseClick = -1;