reflect: add CanInt() and friends and uncomments tests that pass

src/reflect/all_test.go

@@ -430,6 +430,8 @@ func TestMapIterSet(t *testing.T) {
 	}
 }
 
+*/
+
 func TestCanIntUintFloatComplex(t *testing.T) {
 	type integer int
 	type uinteger uint
@@ -617,8 +619,6 @@ func TestCanSetField(t *testing.T) {
 	}
 }
 
-*/
-
 var _i = 7
 
 var valueToStringTests = []pair{