Fix compilation on 32-bit archs (#465)

src/github.com/dgraph-io/ristretto/sketch_test.go:67:8: cannot use 12 << 30 (untyped int constant 12884901888) as int value in assignment (overflows)
src/github.com/dgraph-io/ristretto/store_test.go:209:23: cannot use 4340958203495 (untyped int constant) as int value in argument to z.KeyToHash (overflows)

Author: jas4711

sketch_test.go

@@ -64,7 +64,7 @@ func TestSketchClear(t *testing.T) {
 }
 
 func TestNext2Power(t *testing.T) {
-	sz := 12 << 30
+	sz := int64(12) << 30
 	szf := float64(sz) * 0.01
 	val := int64(szf)
 	t.Logf("szf = %.2f val = %d\n", szf, val)

store_test.go

@@ -206,7 +206,7 @@ func TestStoreExpiration(t *testing.T) {
 	require.True(t, s.Expiration(key).IsZero())
 
 	// missing item
-	key, _ = z.KeyToHash(4340958203495)
+	key, _ = z.KeyToHash(int64(4340958203495))
 	ttl = s.Expiration(key)
 	require.True(t, ttl.IsZero())
 }