patch 8.1.1518: crash when setting 'columns' while a popup is visible

Problem:    Crash when setting 'columns' while a popup is visible.
Solution:   Recompute all positions when clearing the screen. (closes #4467)
diff --git a/src/version.c b/src/version.c
index 7a66295..7432f70 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1518,
+/**/
     1517,
 /**/
     1516,