Qt4 - VLM. enable/disable from the list controls the VLM. small fixes and correction of VLM requests.

BEWARE: If you have non-recompiled plugins, they WILL crash.

 - remove useless IsSubmodule (submodules have NO configuration items anyway, and any sensible UI won't show modules with no configuration)
 - free checks for NULL anyway

* modules/gui/wxwidgets: fix breakage introduced by changeset 23581 and 23579. Breaking perfectly working modules just because you don't care about them is just rude.

Add OpenPGP code, still unused as there is no download of binaries at the moment

We will need to define (and write) the files (and their location) we will use in the update system:

    * We will use a file per arch, which will be signed
    * ALL VideoLAN gpg public keys will be stored on http://download.videolan.org/pub/keys/XXXXXXXXXXXXXXXX.asc where XXXXXXXXXXXXXXXX is the long id of the key
    * Every downloadable file will be signed with gpg --sign --detach --armor

modules/macosx/prefs_widgets.m: module_GetConfig doesn't accept second arg as NULL, quickly work around that.

modules/gui/macosx/prefs*.m: Fix for module_t privatization. Feel free to test. That code is unreadable.

control/media_descriptor.c: As requested by Jacques Boileau, allow options tuning from the media_descriptor class. This is done through libvlc_media_descriptor_add_option.