Enforce strict prototypes

i3 will now compile with no warnings when -Wstrict-prototypes is used.

src/config.c

@@ -32,7 +32,7 @@ void ungrab_all_keys(xcb_connection_t *conn) {
  * Sends the current bar configuration as an event to all barconfig_update listeners.
  *
  */
-void update_barconfig() {
+void update_barconfig(void) {
     Barconfig *current;
     TAILQ_FOREACH(current, &barconfigs, configs) {
         ipc_send_barconfig_update_event(current);

src/x.c

@@ -1254,7 +1254,7 @@ void x_set_name(Con *con, const char *name) {
  * Set up the I3_SHMLOG_PATH atom.
  *
  */
-void update_shmlog_atom() {
+void update_shmlog_atom(void) {
     if (*shmlogname == '\0') {
         xcb_delete_property(conn, root, A_I3_SHMLOG_PATH);
     } else {