patch 9.0.0518: virtual text highlight starts too early with 'nowrap'

Problem:    Virtual text highlight starts too early with 'nowrap' and 'number'
            set.
Solution:   Add the offset to the attribute skip count. (issue #11138)

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    518,
 /**/
     517,
 /**/