xfce4-whiskermenu-plugin: update to latest git

Upstream patch [1] fixes not only mentionend corner bug but makes menu working
with touch devices. First I tried to backport but this seemed more effort than
expected. As soon as another release is out a patch will be send to update.

[1] https://bugzilla.xfce.org/show_bug.cgi?id=11908



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