test: make interval.test tap-compatible

NO_DOC=internal
NO_CHANGELOG=internal

test/unit/interval.c

 #include <stdio.h>
 #include <assert.h>
 
-#include "unit.h"
 #include "string.h"
 #include "datetime.h"
 #include "mp_interval.h"
 
+#define UNIT_TAP_COMPATIBLE 1
+#include "unit.h"
+
 enum {
 	SIZE = 512,
 };

test/unit/interval.result

-1..21
-ok 1 - Size of interval is 3
-ok 2 - Size of interval is 6
-ok 3 - Size of interval is 9
-ok 4 - Size of interval is 12
-ok 5 - Size of interval is 18
-ok 6 - Size of interval is 24
-ok 7 - Intervals are equal.
-ok 8 - Intervals are equal.
-ok 9 - Intervals are equal.
-ok 10 - Intervals are equal.
-ok 11 - Intervals are equal.
-ok 12 - Intervals are equal.
-ok 13 - Year value is right
-ok 14 - Month value is right
-ok 15 - Week value is right
-ok 16 - Day value is right
-ok 17 - Hour value is right
-ok 18 - Minute value is right
-ok 19 - Second value is right
-ok 20 - Nanosecond value is right
-ok 21 - Adjust value is right