Use :select/:deselect signals for consistency

Instead of having a handler on 2 separate objects, use :select and
:deselect on the same one.  Those signals are appropriate, as the
documentation mentions that submenus are popped up on :select.

data/geany.glade

@@ -6321,7 +6321,6 @@
               <object class="GtkMenuBar" id="menubar1">
                 <property name="visible">True</property>
                 <property name="can_focus">False</property>
-                <signal name="deactivate" handler="on_menubar1_deactivate" after="yes" swapped="no"/>
                 <child>
                   <object class="GtkMenuItem" id="file1">
                     <property name="visible">True</property>
@@ -6563,7 +6562,8 @@
                     <property name="can_focus">False</property>
                     <property name="label" translatable="yes">_Edit</property>
                     <property name="use_underline">True</property>
-                    <signal name="activate" handler="on_edit1_activate" swapped="no"/>
+                    <signal name="select" handler="on_edit1_select" swapped="no"/>
+                    <signal name="deselect" handler="on_edit1_deselect" swapped="no"/>
                     <child type="submenu">
                       <object class="GtkMenu" id="edit1_menu">
                         <property name="can_focus">False</property>

src/callbacks.c

@@ -183,7 +183,7 @@ static void on_file1_activate(GtkMenuItem *menuitem, gpointer user_data)
 
 
 /* edit actions, c&p & co, from menu bar and from popup menu */
-static void on_edit1_activate(GtkMenuItem *menuitem, gpointer user_data)
+static void on_edit1_select(GtkMenuItem *menuitem, gpointer user_data)
 {
 	GtkWidget *item;
 	GeanyDocument *doc = document_get_current();
@@ -200,9 +200,9 @@ static void on_edit1_activate(GtkMenuItem *menuitem, gpointer user_data)
 }
 
 
-static void on_menubar1_deactivate(GtkMenuShell *menushell, gpointer user_data)
+static void on_edit1_deselect(GtkMenuShell *menushell, gpointer user_data)
 {
-	/* we re-enable items that were disabled in on_edit1_activate() on menu popdown to
+	/* we re-enable items that were disabled in on_edit1_select() on menu popdown to
 	 * workaround mutli-layout keyboard issues in our keybinding handling code, so that
 	 * GTK's accelerator handling can catch them.
 	 * See https://github.com/geany/geany/issues/1368#issuecomment-273678207 */