contribs: force --target, --build and --host whether cross compiling or not to get around some configure script bugs

Doesn't lock the playlist if unneeded

* Quick fix when transcoding and resampling mono audio tracks.
* The transcode module should be reviewed: all the the fields in p
_enc->fmt_in are not set, it seems 

Comment unusued artist & album musicbrainz ids

Thanks to Daniel Stränger

Detect audio and video on CD-R and DVD-R mediums

Still not functionnal and ugly code.

* + a const fix

* configure.ac: when we use the packed attribute we really mean it so don't output useless compilation warnings.

* 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

* vlc.win32.nsi.in: Add shortcuts in seperate Utilities menu through the installer for easy access to main aout, vout and intf switches. Add NEWS.txt as Release Notes.

 - 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