Use strict function prototypes

Fixes clang error:
error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]

glfw/dbus_glfw.c

@@ -174,7 +174,7 @@ glfw_dbus_dispatch(DBusConnection *conn) {
 }
 
 void
-glfw_dbus_session_bus_dispatch() {
+glfw_dbus_session_bus_dispatch(void) {
     if (session_bus) glfw_dbus_dispatch(session_bus);
 }
 
@@ -344,7 +344,7 @@ glfw_dbus_connect_to_session_bus(void) {
 }
 
 DBusConnection *
-glfw_dbus_session_bus() {
+glfw_dbus_session_bus(void) {
     if (!session_bus) glfw_dbus_connect_to_session_bus();
     return session_bus;
 }