Whitelist constructors aliasable to core-js

Expand the list of identifiers for which we substitute `_core.<Something>`
for `<Something>`.  Also an alternative fix for #421.

test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js

@@ -0,0 +1,7 @@
+obj.constructor === Object;
+obj.constructor === Promise;
+
+Symbol();
+Symbol("test");
+
+new Map();

test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js

@@ -6,5 +6,10 @@ var _interopRequire = function (obj) {
 
 var _core = _interopRequire(require("core-js/library"));
 
-_core.Symbol("test");
+obj.constructor === Object;
+obj.constructor === _core.Promise;
+
 _core.Symbol();
+_core.Symbol("test");
+
+new _core.Map();

test/fixtures/transformation/optional-core-aliasing/ignore-natives/actual.js

@@ -1 +0,0 @@
-obj.constructor === Object;

test/fixtures/transformation/optional-core-aliasing/ignore-natives/expected.js

@@ -1,9 +0,0 @@
-"use strict";
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-obj.constructor === Object;

test/fixtures/transformation/optional-core-aliasing/map-symbol/actual.js

@@ -1,2 +0,0 @@
-Symbol("test");
-Symbol();