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/test41.c

@@ -15,9 +15,10 @@
 #include <errno.h>
 
 #define ITERATIONS 3
-#define MAX_ERROR 4
+int max_error = 4;
+#include "common.h"
+
 
-#include "common.c"
 
 /* we have to keep in mind the millisecond values are rounded up */
 #define UPPERUSEC(us) ((us)+(1000000/system_hz))