Redo Package.swift for Swift Package Manager 4.0.

runtime/Swift/Package.swift

@@ -1,3 +1,4 @@
+// swift-tools-version:4.0
 // Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 // Use of this file is governed by the BSD 3-clause license that
 // can be found in the LICENSE.txt file in the project root.
@@ -5,15 +6,19 @@
 import PackageDescription
 
 let package = Package(
-    name: "Antlr4"
-)
-
-products.append(
-    Product(
-        name: "Antlr4",
-        type: .Library(.Dynamic),
-        modules: [
-            "Antlr4"
-        ]
-    )
+    name: "Antlr4",
+    products: [
+        .library(
+            name: "Antlr4",
+            type: .dynamic,
+            targets: ["Antlr4"]),
+    ],
+    targets: [
+        .target(
+            name: "Antlr4",
+            dependencies: []),
+        .testTarget(
+            name: "Antlr4Tests",
+            dependencies: ["Antlr4"]),
+    ]
 )