remove warning about libvlc and libvlc-control not being valid plugins

extras/contrib/src/Makefile: Fix dca an zvbi install name (on Mac OS X in particular). (Reported by maru).

We now have:
 1x 1.5x 2x 3x 4x 8x (and the same for slower).

MacOSX/Framework/VLCLibrary.m: Regroup the sharedLibrary allocation and release. Fix a warning due to a left over in previous commit.

MacOSX/Framework/VLCLibrary.m: Better memory management for the global VLCLibrary object. Give an autoreleased object in +[VLCLibrary sharedLibrary]. Release the global VLCLibrary atexit.

Destroying the instance object while a descriptor is still alive will crash(!).
I wonder why libvlc_instance_t is not reference counted as the other handler types... ?

Changing the order of parameters may be needed, but changing the parameters themselves is definitely not (it would crash in some cases anyway): add some const qualifiers

 * add missing const qualifiers
 * prevent exception from being silented in case of ENOMEM

Qt4 - Simple prefs, re-do [22621], but removes all the connects for all the configcontrol, remove some functions, clean it, remove some dynamic_cast, but basically do the same.

New inhibit module to prevent the power management daemon (usually gnome-power-manager) to suspend/hibernate the laptop while VLC is active.