Update to swift-DEVELOPMENT-SNAPSHOT-2016-05-03-a

atpkg @ a846230a

-Subproject commit b42022731e191cbe5d038a0d624caf5d1de2a271
+Subproject commit a846230a116de646ec15ff5bc031de563b07fc11

attools/src/CustomTool.swift

@@ -13,7 +13,7 @@ final class CustomTool: Tool {
     }
     let name: String
     init(name: String) {
-        self.name = String(name.characters[name.characters.startIndex..<name.characters.startIndex.advanced(by: name.characters.count - 7)])
+        self.name = String(name.characters[name.characters.startIndex..<name.characters.index(name.characters.startIndex, offsetBy: name.characters.count - 7)])
     }
     func run(task: Task, toolchain: String) {
         var cmd = "\(self.name) "