patch 8.0.0546: swap file exists briefly when opening the command window

Problem:    Swap file exists briefly when opening the command window.
Solution:   Set the noswapfile command modifier before splitting the window.
            (James McCoy, closes #1620)
diff --git a/src/version.c b/src/version.c
index 4d386ee..8f50ac5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    546,
+/**/
     545,
 /**/
     544,