skins2: For Linux, correct files that cannot be loaded because of a workaround that only makes sense on Windows.

Forcefully setting a file name with lower case was inserted to solve an issue that is only true on Windows. On Linux, upper/lower case must not be tampered with.
This resulted in skins like Orangeade.vlt failing to load their fonts on Linux.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

CID 140

  Martin Michlmayr; Debian #417750.

 - use utf8_(read|open)dir
 - do not assume that stat() succeeds (tiny race condition)

   possible to load a skin on Windows when logged with an account containing
   non-english characters.

 Now it starts to really look cool ;-)
* builder.cpp: look for fonts in the resource path if the
 font file cannot be found in the theme itself
* ctrl_slider.cpp: fixed the hack for winamp: the bar images
 are separated by 2 rows, not 3...

   when the extraction failed

 depends on the position of the slider. The "Slider" elements now
 have optional attributes "background", which the Id of a bitmap,
 and "nbimages" which is the number of images in the bitmap (it
 is similar to the radialslider). At the moment there is a hack
 to support winamp slider bars: the different images must be
 separated by 3 rows of unused pixels (well, maybe they are
 useful; if someone knows how... ;)
* theme_loader.cpp: convert the file names from zip archives to 
  lower case, to avoid mixed case issues in some winamp skins

 * skins2/src/theme_loader.cpp: Fixed another directory delimiter issue. The winamp skins load perfectly on windows now...

* theme_loader.cpp: correct handling of subdirectories in winamp
  skins

 lot of things to do but it works !
* theme_loader.cpp: when a theme contains no XML file, assume
 we are trying to load a winamp skin, and use winamp2.xml
* vlcproc.cpp: repaired text variables ($N was broken)

  Borrowed code from Gilles Vollant for the unzip part
  (I guess this code should be put elsewhere in vlc, but it was
  the easy way for me at the moment;) I hope it compiles fine
  everywhere, I've tested only on linux.
  Now, everything's ready for winamp skins ;)

  does what it should (if set to "false", the window is hidden
  when the theme is loaded for the first time)

Fix 64 bits build (Debian #324031)

(da big courmischage)

* src/extras/dirent.c, ALL: fixed win32/ce dirent replacement and made it accessible from plugins as well.

* modules/gui/skins2/src/theme_loader.cpp: portability fix (gzopen_frontend() is still borked on 64bits platforms).

   (the new vout is refreshed)