patch 9.0.0346: :horizontal modifier not fully supported

Problem:    :horizontal modifier not fully supported.
Solution:   Also use :horizontal for completion and user commands.
            (closes #11025)

src/version.c

@@ -707,6 +707,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    346,
 /**/
     345,
 /**/