[BigIntModule] Add copyright headers and update an outdated comment.

Package.swift

@@ -3,7 +3,7 @@
 //
 // This source file is part of the Swift Numerics open source project
 //
-// Copyright (c) 2019 Apple Inc. and the Swift Numerics project authors
+// Copyright (c) 2019-2020 Apple Inc. and the Swift Numerics project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

Sources/BigIntModule/BigInt.Words.swift

@@ -1,3 +1,14 @@
+//===--- BigInt.Words.swift -----------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 extension BigInt {
   /// The words of an arbitrarily large signed integer.
   ///

Sources/BigIntModule/BigInt._Significand.swift

@@ -1,3 +1,14 @@
+//===--- BigInt._Significand.swift ----------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 extension BigInt {
   /// The significand of a `BigInt` value, a nonempty collection of the
   /// significant digits of that value's magnitude stored in words of type
@@ -67,7 +78,7 @@ extension BigInt._Significand: RandomAccessCollection, MutableCollection {
   }
 }
 
-/// `BigInt._Coefficient` can never be empty, so it cannot conform to
+/// `BigInt._Significand` can never be empty, so it cannot conform to
 /// `RangeReplaceableCollection`; however, we will implement some of its
 /// requirements here.
 ///

Sources/BigIntModule/BigInt.swift

@@ -1,3 +1,14 @@
+//===--- BigInt.swift -----------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 /// An arbitrarily large signed integer.
 ///
 /// Because there is no logical minimum or maximum value representable as a

Sources/BigIntModule/BinaryInteger.swift

@@ -1,3 +1,14 @@
+//===--- BinaryInteger.swift ----------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 extension BinaryInteger {
   @inlinable
   internal mutating func _invert() {

Sources/BigIntModule/RandomNumberGenerator.swift

@@ -1,3 +1,14 @@
+//===--- RandomNumberGenerator.swift --------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 extension RandomNumberGenerator {
   @usableFromInline // @inlinable
   internal mutating func _next(upperBound: BigInt) -> BigInt {

Sources/Numerics/Numerics.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift Numerics open source project
 //
-// Copyright (c) 2019 Apple Inc. and the Swift Numerics project authors
+// Copyright (c) 2019-2020 Apple Inc. and the Swift Numerics project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

Tests/BigIntTests/AttaswiftBigInt.swift

@@ -1,3 +1,14 @@
+//===--- AttaswiftBigInt.swift --------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 import BigInt
 typealias AttaswiftBigInt = BigInt
 typealias AttaswiftBigUInt = BigUInt

Tests/BigIntTests/BigIntTests.swift

@@ -1,3 +1,14 @@
+//===--- BigIntTests.swift ------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Numerics open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift Numerics project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
 import XCTest
 @testable import BigIntModule