Update the way of working of the coverage so that it produces

more useful information about the line coveraged, and avoid
expanding low level macros.

tests/test-msnapshot.c

@@ -21,11 +21,15 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 #include <gmp.h> // For testing purpose only.
+
 #include "m-snapshot.h"
 
+#include "coverage.h"
+START_COVERAGE
 SNAPSHOT_DEF(uint, unsigned int)
 SNAPSHOT_DEF(mpz, mpz_t,
              (INIT(mpz_init), INIT_SET(mpz_init_set), SET(mpz_set), CLEAR(mpz_clear)))
+END_COVERAGE
 
 static void test_uint(void)
 {