Log Message:
Update wip/xfce4-panel to 4.8.6.

Upstream changes:

4.8.6
=====
- Panel: Wait until the wm is ready on all screens (bug #7161).
- Systray: Control the thinkness of the frame (bug #7593).
- Launcher: Fix broken compilation (bug #7966).
- Launcher: Don't reconstruct the items on save (bug #7952).
- Applicationsmenu: Fix segfault with not-existing menu (bug #7895).
- Libxfce4panel: Avoid problem if panel is not yet realized.
- Panel: Print string in case of an invalid position.
- Libxfce4panel: Always try to return an icon.
- Directorymenu: Also send the target directory as arg (bug #7745).
- Translation updates (it, tr, nl, sk, pt_BR, te, zh_CN, pt, ru, ko,
  ja, ro, fr, kk, ms, es, id, eu).