patch 9.0.1512: inserting lines when scrolling with 'smoothscroll' set

Problem:    Inserting lines when scrolling with 'smoothscroll' set.
Solution:   Adjust line height computation for w_skipcol. (Luuk van Baal,
            closes #12350)
diff --git a/src/version.c b/src/version.c
index 9f4a449..08f213a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1512,
+/**/
     1511,
 /**/
     1510,