Clarify comment of _nonSendable with a message explaining the remaini…

…ng warning

Sources/Foundation/Formatter.swift

@@ -43,7 +43,7 @@ extension Formatter {
     }
 }
 
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class Formatter : NSObject, NSCopying, NSCoding {
 
     public override init() {

Sources/Foundation/NSCoder.swift

@@ -100,7 +100,7 @@ public protocol NSSecureCoding : NSCoding {
 /// is normally of the same class as the object that was originally encoded into
 /// the stream. An object can change its class when encoded, however; this is
 /// described in Archives and Serializations Programming Guide.
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class NSCoder : NSObject {
     internal var _pendingBuffers = Array<(UnsafeMutableRawPointer, Int)>()
 

Sources/Foundation/NSEnumerator.swift

@@ -10,7 +10,7 @@
 @available(*, unavailable)
 extension NSEnumerator.Iterator : Sendable { }
 
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class NSEnumerator : NSObject {
 
     open func nextObject() -> Any? {

Sources/Foundation/NSObject.swift

@@ -152,7 +152,7 @@ extension NSMutableCopying {
 }
 
 /// The root class of most Foundation class hierarchies.
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class NSObject : NSObjectProtocol, Equatable, Hashable {
     // Important: add no ivars here. It will subvert the careful layout of subclasses that bridge into CF.
 

Sources/Foundation/Port.swift

@@ -18,7 +18,7 @@ extension Port {
     public static let didBecomeInvalidNotification  = NSNotification.Name(rawValue: "NSPortDidBecomeInvalidNotification")
 }
 
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class Port : NSObject, NSCopying {
     /// On Darwin, you can invoke `Port()` directly to produce a `MessagePort`. Since `MessagePort` is not available in swift-corelibs-foundation, you should not invoke this initializer directly. Subclasses of `Port` can delegate to this initializer safely.
     public override init() {

Sources/Foundation/Stream.swift

@@ -55,7 +55,7 @@ extension Stream {
 
 // Stream is an abstract class encapsulating the common API to InputStream and OutputStream.
 // Subclassers of InputStream and OutputStream must also implement these methods.
-//@_nonSendable
+//@_nonSendable - TODO: Mark with attribute to indicate this pure abstract class defers Sendable annotation to its subclasses.
 open class Stream: NSObject {
 
     public override init() {