xfce4-xkb-plugin: Update to latest git

In 7b35cdc5 xfce4-settings was updated to
development-release 4.11.0. Reason for this was handling of keyboard layout
by xfce4-settings.
With this patch xfce4-xkb-plugin synchronizes with xfce4-settings, shares
settings and uses dialogs from xfce4-settings. These changes were not yet
released because they depend on development-release of xfce4-settings.
Next stable release of xfce4-settings will be with xfce 4.12 with release date
unknown [1].

[1] http://wiki.xfce.org/releng/4.12/roadmap#roadmapplanned_features



Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>