so that it is cleanly built before all modules
  (step toward buildable shared libvlc on Win32)
- Don't build position dependant code when building shared libvlc
  (that was a big waste of time)
- Link builtin modules with vlc rather than libvlc

- Hopefully the same on Darwin

!!! BIG FAT WARNING !!!
On architectures where you need to resolve all symbols when
linking a shared library, libvlc must be built before the plugins, so
that they can resolve symbols from the libvlc API. Also, the "builtins"
must be built before libvlc (regardless of the architecture or use of
shared libvlc). However, our build system currently builds all modules,
whether builtins or plugins, then libvlc and then vlc.

Obviously, we could swap the build orders, so that libvlc gets built
before modules/ but that will only work if there is no buitins modules.
I'm not too keen on the idea of recursing twice within the modules/
subdirectories (once for builtins, and once for plugins). Until the
issue is settled, here is how to build and test the shared libvlc on
Win32:

1/ run configure with --enable-shared-libvlc
2/ build all built-in modules (or disable them all) one by one,
3/ make libvlc.dll
4/ make

tested with 
./vlc --sub-filter rss --rss-urls "http://www.lefigaro.fr/rss/figaro_une.xml|http://newsrss.bbc.co.uk/rss/newsonline_world_edition/front_page/rss.xml" --rss-length 40 --rss-size 15 --rss-images --rss-speed 1000 <video>

Add with-ffmpeg-{vorbis,theora,ogg} in case ffmpeg is compiled with vorbis, theora and/or ogg support

- the actual download is currently done by your default browser since the needed notification window isn't available on OSX yet
    - download through VLC is implemented, but commented for the moment
- needs some checking once a complete Status.xml is available

image.c: ImageReadUrl now tries to open the image using the stream functions if fopen failed. (Which means that it can now read images on the web)

(we don't seem to be). ${LIBINTL} is normally not defined when there is
no libintl anyway - should fix FreeBSD libintl linking issue

method. It's still quite simple ... loads of room for improvement.
Example available here: http://people.videolan.org/~dionoea/bluescreen.mpg

* mosaic.h: remove trailing space

  This might explain the audio-core crashes we have seen in the past on Mac OS X 
* Fix issues with platforms which don't have alloca() (defined)