The download specific functions should maybe be exported (i don't know if
other modules would need to download files to disk)

zorglub: could you have a look ? this solution doesn't seem right to
me because we "loose" some of the calls to the interaction system if
they're sent at the wrong moment.

* Reduce vlc_object_find calls

modules/gui/wxwidgets/dialogs/updatevlc.cpp : clean up

(i just had to find the suxor thread exemple in video_output.c :p )

                   to use in interfaces)
                   The downloadable plugins part still needs some work.

modules/control/rc.c : add function to query updates (mainly used for testing)

modules/gui/wxwidgets/* : update pannel.