* include/vlc_playlist.h

* include/vlc_playlist.h
  src/playlist/playlist.c:
     * Implemented a boolean b_enabled to disable a playlist item
     * Implemented the idea of group (p_item->i_group), that allows
       to enable/disable and to sort some series of items
     * Implemented an unused (at the moment), psz_author field
     * Started to implement a new playlist format to store all of these

* modules/gui/wxwindows/interface.cpp:
     Added a hiddeable panel to put some important options.
     (Menu Preferences->Extra GUI)
     At the moment, we put the adjust filter and aspect ratio, and must
     decide what options we want here

* modules/gui/wxwindows/playlist.cpp
  modules/gui/wxwindows/iteminfo.cpp:
     Added "Enable/disable group button", options to enable/disable selection
     Added an item info dialog box

* modules/misc/sap.c :
     Added a sap-group-id option: the SAP playlist items are in a separate group
     (defaults to 42)

* modules/visualization/visual/effects.c:
     Minor coding style fixes

Todo:
-----

* Advanced sort (alphabetical and/or by group)
* Ability to load 0_6 playlists
* Really use the libid3tag