[gnome-calculator] Use set_accels_for_action instead of deprecated add_accelerator

[Robert Roth <robertroth src gnome org>]

commit 5a8d4f89cef9087bac79e3b5c6a1f88298bd08c4
Author: Robert Roth <robert roth off gmail com>
Date:   Fri Jan 26 21:52:40 2018 +0200

    Use set_accels_for_action instead of deprecated add_accelerator

 src/gnome-calculator.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gnome-calculator.vala b/src/gnome-calculator.vala
index d261d3a..9f2549e 100644
--- a/src/gnome-calculator.vala
+++ b/src/gnome-calculator.vala
@@ -75,7 +75,7 @@ public class Calculator : Gtk.Application
         Number.precision = precision;
 
         add_action_entries (app_entries, this);
-        add_accelerator ("<Primary>Escape",  "win.clear", null);
+        set_accels_for_action ("win.clear", {"<Primary>Escape"});
 
         var current_window = new MathWindow (this, equation);
         current_window.set_title (_("Calculator"));