Update Dutch translation

Signed-off-by: Reinout Hoornweg <reinout@xs4all.nl>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't use gtk_show_about_dialog() for the about dialog

There is a bug in GTK 2.2x where the links in the about dialog
(and URI's in general) do not work on Windows. To solve that
we add the OS specific method subsurface_launch_for_uri().
But to dispatch URI requests from the about dialog we need to
set a hook either with gtk_about_dialog_set_url_hook() (which is
deprecated from 2.24) or using signals like "activate-link".

One problem with the "activate-link" signal thought is that
we need to have a reference of an about dialog to pass to
g_signal_connect(). So instead of using gtk_show_about_dialog()
let's manage a dialog ourself with gtk_about_dialog_new(),
gtk_dialog_run(), gtk_widget_destroy().

Other changes:
- for GTK _bellow_ (but not including) 2.24 use
gtk_about_dialog_set_url_hook()
- use g_object_set() which is a convenient replacement for
the varargs list in gtk_show_about_dialog() (also makes the diff smaller).

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>