lavd/fbdev_common: fix compilation with older kernels

This will avoid errors due to conflicting declarations
with linux kernels prior to 2.6.30.
Reviewed-by: Lukasz M <lukasz.m.luki@gmail.com>
Signed-off-by: Ingo Brückl <ib@wupperonline.de>

libavdevice/fbdev_common.h

@@ -23,6 +23,7 @@
 #ifndef AVDEVICE_FBDEV_COMMON_H
 #define AVDEVICE_FBDEV_COMMON_H
 
+#include <features.h>
 #include <linux/fb.h>
 #include "libavutil/pixfmt.h"