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)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    546,
 /**/
     545,
 /**/