Include config.h in all .c files

Need to be the first file since it may define large files support
and other options.

src/libmdb/data.c

@@ -16,9 +16,10 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#include "config.h"
+#include <time.h>
+#include <math.h>
 #include "mdbtools.h"
-#include "time.h"
-#include "math.h"
 
 #ifdef DMALLOC
 #include "dmalloc.h"