patch 8.1.1602: popup window cannot overflow on the left or right

Problem:    Popup window cannot overflow on the left or right.
Solution:   Only set the "fixed" option when it is in the dict. Set w_leftcol
            to allow for the popup overflowing on the left and use it when
            applying the mask.
diff --git a/src/version.c b/src/version.c
index 55c62df..d44171d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1602,
+/**/
     1601,
 /**/
     1600,