Fix 64 bits build (Debian #324031)

 * skin_parser.cpp : add comment so people know where to look to fix the
                     Playlist slider breakage.

Slower maybe, but safer
and arguably more suited for automatically issued tarballs

(wanted to cancel, but I pressed the wrong key)

bootstrap might be a little slower,
but that'll ensure more recent build-system in tarballs.
Besides, 

   work, cleaning and fixing. I'll continue this weekend.

 * playtree.vlt : default.vlt modified to use a Playtree instead of a
                  Playlist

   is in reality the name of the file (compatibility with existing
   m3u files).

   indicate which object we are playing with (for instance 'VLC_OBJECT_INPUT'
   or 'VLC_OBJECT_PLAYLIST'). Espace \ in addslashes.
 * modules/control/http: Factorized and simplified the RealPath() stuff.
   Fixed a few hardcoded '/' as a path separator.

Fix region width/height encoding bug. Dvbsub never tested for a change in region widht/height that made a region smaller then the previous one that was encoded. The encoded region size would always been the largest size encountered, this is now fixed. Removed some superflous whitespace/

Improve documentation
Enable build of modules documentation

Fix an issue with the state option (behaves differently then in 0.8.1) and removed useless white space.

* get the correct vout, when using the opengl-output-module - on-the-fly changing still not possible

It was probably too easy that building to Windows and Linux worked the same

Added --volume-step to override AOUT_VOLUME_DEFAULT. This will give an OSD menu (or skins2) designer to freedom to decide how many steps he wants for turning up the volume from 0 to 1024. It is an advanced option so most users will never see it. Can someone check the MacOSX changes for this? I made them but cannot compiler and test it (I don't have a Mac).

* set the 'auto save name' for the equalizer, extended and bookmarks panels to automatically save their positions (closes #316)