get rid of non-ANSI function declarations missing (void)

Detected by Smatch
diff --git a/src/vty/vty.c b/src/vty/vty.c
index a1f0304..1f3237a 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -45,7 +45,7 @@
 }
 
 /* Allocate new vty struct. */
-struct vty *vty_new()
+struct vty *vty_new(void)
 {
 	struct vty *new = talloc_zero(tall_vty_ctx, struct vty);
 
@@ -1591,7 +1591,7 @@
 };
 
 /* Reset all VTY status. */
-void vty_reset()
+void vty_reset(void)
 {
 	unsigned int i;
 	struct vty *vty;
@@ -1631,7 +1631,7 @@
 	strcpy(vty_cwd, cwd);
 }
 
-char *vty_get_cwd()
+char *vty_get_cwd(void)
 {
 	return vty_cwd;
 }
@@ -1641,7 +1641,7 @@
 	return vty->type == VTY_SHELL_SERV ? 1 : 0;
 }
 
-void vty_init_vtysh()
+void vty_init_vtysh(void)
 {
 	vtyvec = vector_init(VECTOR_MIN_SIZE);
 }