patch 8.2.0844: text properties crossing lines not handled correctly

Problem:    Text properties crossing lines not handled correctly.
Solution:   When saving for undo include an extra line when needed and do not
            adjust properties when undoing. (Axel Forsman, closes #5875)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    844,
 /**/
     843,
 /**/