Remove unused avdevice.h header file; add config.h which is used.

Originally committed as revision 13006 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavdevice/alldevices.c

@@ -18,7 +18,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include "avformat.h"
-#include "avdevice.h"
+#include "config.h"
 
 #define REGISTER_MUXER(X,x) { \
           extern AVOutputFormat x##_muxer; \