xfce4-panel: enable StatusNotifier support.

The Status Tray plugin then works properly for applications using the
StatusNotifier API. Context:
- https://github.com/J-Lentz/iwgtk/issues/21
- https://forum.xfce.org/viewtopic.php?pid=65399#p65399

srcpkgs/xfce4-panel/template

@@ -1,13 +1,14 @@
 # Template file for 'xfce4-panel'
 pkgname=xfce4-panel
 version=4.16.3
-revision=1
+revision=2
 build_style=gnu-configure
 build_helper="gir"
 configure_args="--with-locales-dir=/usr/share/locale
  --disable-static --enable-gio-unix --enable-gtk3"
 hostmakedepends="xfce4-dev-tools pkg-config intltool gettext-devel glib-devel"
-makedepends="libwnck-devel libxfce4ui-devel xfconf-devel garcon-devel exo-devel"
+makedepends="libwnck-devel libxfce4ui-devel xfconf-devel garcon-devel exo-devel
+ libdbusmenu-gtk3-devel"
 short_desc="Next generation panel for the XFCE desktop environment"
 maintainer="Orphaned <orphan@voidlinux.org>"
 license="GPL-2.0-or-later"