Move child in its original parent if no destination child is found. Show all children before waiting the child move.

src/clfswm-internal.lisp (place-frames-from-xinerama-infos): handle better no xinerama support case.

src/clfswm.lisp (main-mode: configuer request): Call *root-size-change* hook on each root size change. This let CLFSWM refresh background wallpaper on root size changes.

src/clfswm-internal.lisp (place-frames-from-xinerama-infos): Handle root screen resize on the fly when adding or removing a monitor.

src/clfswm-menu.lisp (open-menu): Show key bindings correspondence in menu for main and second mode.