[Documentation] Add doc comments for NSObject

[broadwaylamb]

This pull request adds documentation comments for the following public/open declarations:

Classes:

Protocols:

• NSObject

  • init()
  • copy()
  • mutableCopy()
  • isEqual(_:)
  • hash
  • self()
  • isProxy()
  • description
  • debugDescription
  • _cfTypeID
  • classForCoder
  • replacementObjectForCoder(_:)
  • classForKeyedArchiver
  • replacementObjectForKeyedArchiver(_:)
  • classFallbacksForKeyedArchiver()
  • classForKeyedUnarchiver()
  • hashValue

• NSObjectProtocol

  • isEqual(_:)
  • hash
  • self()
  • isProxy()
  • description
  • debugDescription

• NSCopying

  • copy(with:)
  • copy()

• NSMutableCopying

  • mutableCopy(with:)
  • mutableCopy()

Functions:

• ==(_:_:)

All the comments have been carefully reviewed. The terms referring to Objective-C semantics
have been substituted with ones more appropriate for Swift semantics (e. g. "receiver" → "instance" etc.).

Jazzy	Percentage of documented declarations in Foundation
Before	23%
After	27%

[parkera]

Neat!