Please describe the problem:
At the GTK_VERSION=2.6.x, I could not choice a stock icon named "Forward" 
correctly from Glade UI designer.
It looks that there are two stock icons named "Forward" from this GTK_VERSION;
./gtk/gtkstock.c:282
static const GtkStockItem builtin_items [] =
{
  ...
  { GTK_STOCK_GO_FORWARD, N_("_Forward"), 0, 0, GETTEXT_PACKAGE },
  ...
  { GTK_STOCK_MEDIA_FORWARD, N_("_Forward"), 0, 0, GETTEXT_PACKAGE },
};

Glade (v2.9.0) has also both stock icons in Properties window are appeard.
However, when I pick a "Forward" icon which is considered as 'GTK_STOCK_GO_FORWARD',
it's always set a icon as 'GTK_STOCK_MEDIA_FORWARD'.
I could not choice it as 'GTK_STOCK_GO_FORWARD'.

Steps to reproduce:
1. run `glade-2`.
2. create project "New GTK+ Project".
3. create a Window.
4. pack a Button to Window.
5. pull stock icons list from Properties window.
6. You can see two "Forward" icons.
7. Choice "Forward" as GTK_STOCK_GO_FORWARD, but it's always set as
GTK_STOCK_MEDIA_FORWARD.


Actual results:
I can not pick a "Forward" stock icon as GTK_STOCK_MEDIA_FORWARD from Properties
window.

Expected results:
It looks that Glade can not handle _GtkStockItem::stock_id correctly.


Does this happen every time?
Always on Glade v2.6.0.

Other information: