* 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 a bunch of transition now-useless API.
 - Remove all playlist_Lock* functions. Matching functions now accept a
   b_locked parameter that should be set to VLC_TRUE if the playlist is
   locked when calling the function. The advantages are that it reduces
   the API bloat and that the b_locked flag can be propagated in the
   call stack
 - Remove useless playlist testsuite
 - Remove broken daap plugin (unmaintained wrt VLC API changes, relies on 
   an unmaintained library, probably unable to read content from new itunes, 
   ...). Implementations exist in rhythmbox, xmms2 and 
   daap-sharp, we should see if a proper lib exists or if we could 
   make one
 - Reduce verbosity a bit
 - Documentation

If the item is not to be preparsed but has enough meta, mark it as preparsed

* Remove some unneeded wrappers and locking

This array is now usable as a reliable source of data for size
Use playlist_CurrentSize(p_playlist) to retrieve the size of the current playset.

Not tested heavily yet ...

For interaction implementers: you need to call playlist_Signal after changing the status of a dialog. Please see the diff for qt4/dialogs/interaction.cpp

 * Remove the random special case
 * Use the array of currently playing items for all cases
 * Convert array items to array API
 * Replace standard searches in sorted arrays by bsearches
 * Size is not yet fixed (next round).

Array
 * Add reset/value and bsearch functions
 * Add foreach helper

Correctly count the children of a node. The previous code counted the endpoints too, which gave a too high children count.

Update stats in the input threads instead of playlist thread

Todo: we should recheck cache just before downloading in case it has been downloaded while we were in the queue

Compile fix

 * Secondary queue items now have a b_fetch_art flag
 * You can use the playlist_AskForArtEnqueue function to ask for art from an interface. This will enqueue at the begining of the secondary queue
 * other stuff which i don't remember :)
 * (fix issues with previous (and unrelated) DIR_SEP commit)

* Put meta related functions in src/input/meta.c
* Merge vlc_meta_engine.h and vlc_meta.h

Album art stuff is still broken, but I need to go now :)

* meta reader : read directly from the file, should be made from the demux.
  Examples: taglib, id3tag
* meta fetcher : use web services to get meta, either from the current ones.
  Called only if we don't have the tags after using the meta readers
* art finder : find the URL of the suitable album art. Called according to the
  art policy
* art downloader : used to retrieve the art from special locations. Not needed
  if art is available directly from an URL.
  Examples: APIC ID3 tag reader

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

Add an "album art download policy" (--album-art) option. I now have to do another commit to enfore this policy (album art isn't downloaded at all atm)

Start of meta engine stuff. src/input/input.c needs to be fixed a bit. I'll finish it today. @zorglub: now you have to use the psz_arturl meta to display stuff in the interface.