Add support to the activex, mozilla, firefox, safari plugin for changing audio track and audio output channel (reverse, stereo, left, right, dolby).

 * skins2/src/generic_layout.cpp: Fixed an old memory leak
This is a forwardport of [18282]

* const string fixes 
* make a couple of functions static

- Do not leak result from utf8_readdir (ALWAYS strdup'ed).

* Add some doxygen comments to some of these functions that warn about vlc_closedir_wrapper and LocaleFree

  * utf8_fopen for: galaktos and snapshots
  * vlc_closedir_wrapper for: webintf, mkv, ncurses and gnutls

  - don't compile pngtest, it's not SDK compatible
  - enable sdk on contrib again

 - Only try Real RTSP in case of rtsp:// realrtsp:// or pnm://
 - Don't use fprintf

Someone (I?) ought to work on a better solution

  releasing it. mutex locks /= 20 on a standard preparse run
* Only create absolutely necessary variables while preparsing
--> Preparse speed *= 4 (with item in disk cache of course)

* Do not rebuild playlist too much while adding a directory. Add a new flag
  to NodeCreate and Add to control this behaviour

For some unknown reason, wxwidgets 2.6.3 always return WXK_NUMPAD_DELETE
even in case normal Delete key was pressed

Please consider backporting just for Win32 binaries.

Fix m3u export

This might not fix it, but it surely should eleviate the problem.
forwardport of [18324]