[gnome-shell] na-tray-manager: Add missing `void` to functions with no arguments

[Florian Müllner <fmuellner src gnome org>]

commit 1e3a174de988c29261dbb93fc10fc72974fe5342
Author: Robert Mader <robert mader posteo de>
Date:   Tue Mar 5 23:21:25 2019 +0100

    na-tray-manager: Add missing `void` to functions with no arguments
    
    to avoid "old-style function definition" and "function declaration
    isn’t a prototype" warnings.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/441

 src/tray/na-tray-manager.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/src/tray/na-tray-manager.c b/src/tray/na-tray-manager.c
index fdf47da55..aea42eea2 100644
--- a/src/tray/na-tray-manager.c
+++ b/src/tray/na-tray-manager.c
@@ -70,7 +70,7 @@ static guint manager_signals[LAST_SIGNAL];
 #define SYSTEM_TRAY_ORIENTATION_VERT 1
 
 #ifdef GDK_WINDOWING_X11
-static gboolean na_tray_manager_check_running_screen_x11 ();
+static gboolean na_tray_manager_check_running_screen_x11 (void);
 #endif
 
 static void na_tray_manager_finalize     (GObject      *object);
@@ -808,7 +808,7 @@ na_tray_manager_manage_screen (NaTrayManager *manager)
 #ifdef GDK_WINDOWING_X11
 
 static gboolean
-na_tray_manager_check_running_screen_x11 ()
+na_tray_manager_check_running_screen_x11 (void)
 {
   GdkDisplay *display;
   GdkScreen *screen;
@@ -833,7 +833,7 @@ na_tray_manager_check_running_screen_x11 ()
 #endif
 
 gboolean
-na_tray_manager_check_running ()
+na_tray_manager_check_running (void)
 {
 #ifdef GDK_WINDOWING_X11
   return na_tray_manager_check_running_screen_x11 ();