configure: Use a separate config_components.h header for $ALL_COMPONENTS

This avoids unnecessary rebuilds of most source files if only the
list of enabled components has changed, but not the other properties
of the build, set in config.h.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavdevice/alsa.c

@@ -28,6 +28,8 @@
  * @author Nicolas George ( nicolas george normalesup org )
  */
 
+#include "config_components.h"
+
 #include <alsa/asoundlib.h>
 #include "avdevice.h"
 #include "libavutil/avassert.h"