patch 9.0.1601: filetype detection fails for *.conf file without comments

Problem:    Filetype detection fails for *.conf file without comments.
            (Dmitrii Tcyganok)
Solution:   Use "conf" filetype as a fallback for an empty .conf file.
            (closes #12487, closes #12483)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1601,
 /**/
     1600,
 /**/