add generic dispatcher headers for frontend etc

add generic audio, video and demux headers in zapit/include (TODO: put them
into a better place, or put wrappers into lib directories) that automatically
dispatch to the hardware specific functions and use them in the code

git-svn-id: file:///home/bas/coolstream_public_svn/THIRDPARTY/applications/neutrino-experimental@962 e54a6e83-5905-42d5-8d5c-058d10e6a962

src/gui/videosettings.cpp

@@ -51,7 +51,7 @@
 #include <system/debug.h>
 
 #include <cs_api.h>
-#include <video_cs.h>
+#include <video.h>
 
 extern cVideo *videoDecoder;
 extern int prev_video_mode;