include config.h in all sources

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

test/software_volume.c

@@ -23,6 +23,7 @@
  *
  */
 
+#include "config.h"
 #include "pcm_volume.h"
 #include "audio_parser.h"
 #include "audio_format.h"