patch 7.4.2106

Problem:    Clang warns about missing field in initializer.
Solution:   Define COMMA and use it.  (Kazunobu Kuriyama)

src/version.c

@@ -758,6 +758,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2106,
 /**/
     2105,
 /**/