Re-enables media library.
Fixes #1047 (nth attempt).

And why the heck was this undone in the first place??

On OSes other than Windows, Mac OS X and BeOS (so it's Linux) comply with the XDG Base Directory Specification version 0.6. The old configuration file (vlcrc) will be copied to the new location. Other data like caches will have to be rebuilt (the album art cache in VLC was new in 0.9.0 so it's ok to lose it). Closes #1267

Uses --no-media-library if you don't want to use it (see #1047)

(which is always)

I thought the comments where pretty clear.

* Headers in include must contain the structures and prototypes needed
  by the plugins and should be named vlc_*.
* Headers in include/vlc must contain the structures and prototypes
  needed by external libvlc clients

* Moved and renamed some things in headers. 
   - Removed vlc_cpu.h, vlc_error.h (merged in vlc_common)
   - Removed snapshot.h (merged in vlc_vout.h)
   - Removed vlc_spu.h (merged in vlc_osd.h)
   - Removed intf_eject.h and vlc_interaction.h (merged in vlc_interface)
   - Moved all internal headers to src
   - Merged vlc_video.h and video_output.h and move private things to src
   - Removed vlc/intf.h, vlc/aout.h, vlc/vout.h, vlc/decoder.h and vlc/input.h
     (meta headers for use in modules, and often implying too large 
     dependencies)
* Removed some useless dependencies
* Unexported a bunch of functions and structures used only in src/
  (--> Still some work here)
* Finally made input_thread_t and input_source_t (mostly) private. 
  Added input_GetItem to fetch the input_item of an input_thread
* Cleaned up deprecated entries in vlc_symbols.h and bumped up symbol 
  prefix

This commit has a 99% probability of breaking the build, 0.1% of killing
your cat and 0% of getting you hot chicks.

* Unexported a few internal functions
  (playlist_ItemDelete, playlist_ThreadCreate, playlist_ThreadDestroy)
* Remove playlist_AddSDModules and merge its features into ServicesDiscoveryAdd
* Fix a bug in signaling of node destruction (fixes Qt source selector assertion failures)
* Disable unused generic devices probe code

* Remove some unneeded wrappers and locking

Add input_ItemAddOptionNoDup (unused at the moment)
+ free warning fix

Also, make it clearer what is shared and instance-specific

So,
libvlc_t ==> libvlc_global_t
vlc_t ==> libvlc_int_t (internal instance)

p_object->p_libvlc ==> p_object->p_libvlc_globale
p_object->p_vlc ==> p_object->p_libvlc

VLC_OBJECT_VLC ==> VLC_OBJECT_LIBVLC

And by the way, there is some cleanup required :) (ie, some things are created in the global object instead of the instance-specific one)

What is currently broken:
 * Some playlist demuxers (shout, dvb and pls)
 * DAAP
 * BeOS playlist
 * GPE playlist, I suppose

What has some trouble:
 * Meta handling in several demuxers (most notably TS)
 * Skins2 playlist (doesn't refresh correctly)
 * OS X playlist (see bigben's latest commits)

modules/misc/playlist/*, modules/access/http.c: XSPF playlist support
(read and write) by Daniel Stranger. Many thanks

src/misc/modules.c, src/misc/strings.c, include/vlc_strings.h: string
handling functions.

modules/control/http/*, modules/services_discovery/upnp_intel.cpp: use
these string handling functions.

(da big courmischage)

Change some message severities

* ALL: changed the prototype of module_Need() to accept a "strict" boolean argument.
If "strict" is true and a module name is provided then module_Need() will only look for the specified module
If "strict" is false, then module_Need() will first look for the specified module and if it wasn't found, will continue with the other modules with the same "capability".

much memory, and was inconsistent, especially with input_CreateThread
taking an array of options

* Revert to using array of options

* To add an item with options:
    - either use playlist_ItemNew, ItemAddOption, and then AddItem
      (useful if you don't have all your options in an array)
    - either use playlist_AddExt (use this if all your options are
      already in an array)

* To add an item without options: use playlist_Add

You can still add options after an item has been added by using either
playlist_AddOption or playlist_ItemAddOption

* Attempt to improve API and solve thread safety issues.
  - playlist_Item* functions allow to touch items only.
    p_item->lock must be used when needed
    (playlist_ItemNew, playlist_ItemDelete, playlist_Item*Info,
     playlist_ItemSet* )

  - playlist_ItemGetById and ItemGetByPos give you playlist_items
    for GetByPos, you should have the playlist lock

At the moment, the playlist_Set* and playlist_*Info functions are kept (they work with position) but should be avoided.