patch 8.1.1571: textprop highlight starts too early if just after a tab

Problem:    textprop highlight starts too early if just after a tab.
Solution:   Check if still drawing a previous character. (closes #4558)
diff --git a/src/version.c b/src/version.c
index d71b86e..19b6aa7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1571,
+/**/
     1570,
 /**/
     1569,