patch 8.1.1673: cannot easily find the popup window at a certain position

Problem:    Cannot easily find the popup window at a certain position.
Solution:   Add popup_locate().
diff --git a/src/version.c b/src/version.c
index ea5de7d..07c0d7a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1673,
+/**/
     1672,
 /**/
     1671,