Merge upstream master

Author: Simon Whitaker

Multiset/README.markdown

@@ -51,6 +51,8 @@ Here's the essence of it:
 ``` swift
 public struct Multiset<Element: Hashable> {
   private var storage: [Element: UInt] = [:]
+  
+  public init() {}
 ```
 
 And here's how you'd use this class to create a multiset of strings:

Radix Sort/RadixSort.playground/Contents.swift

@@ -2,6 +2,11 @@
 
 import Cocoa
 
+// last checked with Xcode 9.0b4
+#if swift(>=4.0)
+print("Hello, Swift 4!")
+#endif
+
 // Test Radix Sort with small array of ten values
 var array: [Int] = [19, 4242, 2, 9, 912, 101, 55, 67, 89, 32]
 radixSort(&array)

Radix Sort/Tests/RadixSortTests.swift

@@ -9,6 +9,13 @@
 import XCTest
 
 class RadixSortTests: XCTestCase {
+  func testSwift4() {
+    // last checked with Xcode 9.0b4
+    #if swift(>=4.0)
+      print("Hello, Swift 4!")
+    #endif
+  }
+  
   func testCombSort() {
     let expectedSequence: [Int] = [2, 9, 19, 32, 55, 67, 89, 101, 912, 4242]
     var sequence = [19, 4242, 2, 9, 912, 101, 55, 67, 89, 32]

Radix Sort/Tests/Tests.xcodeproj/project.pbxproj

@@ -179,6 +179,7 @@
 				SDKROOT = macosx;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -220,6 +221,7 @@
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -233,7 +235,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = Swift.Algorithm.Club.Tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -246,7 +248,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/../Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = Swift.Algorithm.Club.Tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};