This should help Doxygen parse VLC headers, and generally makes headers
easier to read. LibVLC already uses a similar approach.

It computes correct crop/ar settings when scaling a video format.

It indicates restrictions on the ES (resolution, bitrate, codec
features...), like the H264 level

Other (audio or video) demux/codecs than real demux can use it

It was duplicated with es_format_t::i_sar_num/den.

 There will be some regressions, I used automatic sed replacement with manual
checks but there was a lot to change.
 It's only the first pass.

It removed a hack where dvb.i_id was used for teletext.

This reverts commit 62b9f5b0.

This improves readability a lot and prevent us from reinventing the wheel.

In the same time add spaces in order to follow code convention.

it, disabled by default)

* libvlc sources and plugins now define __LIBVLC__ and headers exported to
  plugins (ie, include/vlc_*.h) check for this
* libvlc sources use the value of the "libvlc" component in vlc-config instead
  of vlc
* Apply flags directly to "libvlc" in configure.ac - might temporarily break win32 :)