avoid warning about old-style no-param function definition

* daemon/df.c (do_df, do_df_h): Add "void".
* sync.c (do_sync): Likewise.

daemon/df.c

@@ -28,7 +28,7 @@
 #include "actions.h"
 
 char *
-do_df ()
+do_df (void)
 {
   int r;
   char *out, *err;
@@ -49,7 +49,7 @@ do_df ()
 }
 
 char *
-do_df_h ()
+do_df_h (void)
 {
   int r;
   char *out, *err;

daemon/sync.c

@@ -24,7 +24,7 @@
 #include "actions.h"
 
 int
-do_sync ()
+do_sync (void)
 {
   sync ();
   return 0;