patch 8.0.0518: bad fold text when a multi-byte char has a zero byte

Problem:    Storing a zero byte from a multi-byte character causes fold text
            to show up wrong.
Solution:   Avoid putting zero in ScreenLines. (Christian Brabandt,
            closes #1567)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    518,
 /**/
     517,
 /**/