tests cleanup

. make common.o link with the tests instead of being
	  #included as common.c
	. fix warnings about missing prototypes by declaring functions
	  static
	. reduces some duplicated code

Change-Id: Ic2a765d7f5886add5863190efec3fdd2d2ea2137

test/test28.c

@@ -20,10 +20,11 @@
 #include <time.h>
 #include <stdio.h>
 
-#define MAX_ERROR	4
+int max_error = 	4;
+#include "common.h"
+
 #define ITERATIONS      2
 
-#include "common.c"
 
 #define DIRENT0		((struct dirent *) NULL)