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.

src/exclude.c

@@ -22,6 +22,7 @@
  *
  */
 
+#include "config.h"
 #include "exclude.h"
 #include "path.h"