patch 9.0.1607: screenpos() returns wrong row with diff filler lines

Problem:    screenpos() returns wrong row with diff filler lines.
Solution:   Only add filler lines when appropriate.  Also don't add the
            'smoothscroll' marker when w_skipcol is zero. (closes #12485,
            closes #12484)
diff --git a/src/version.c b/src/version.c
index b17b01b..13a537d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1607,
+/**/
     1606,
 /**/
     1605,