[doc] Update link to Objective-C 2.0 manual

[Gerald Pfeifer]

Applied (revision 245375).

Gerald

2017-02-12  Gerald Pfeifer  <gerald@pfeifer.com>
 
	* doc/standards.texi (Standards): Update reference to
	Objective-C 2.0.

Index: doc/standards.texi
===================================================================
--- doc/standards.texi	(revision 245374)
+++ doc/standards.texi	(working copy)
@@ -290,7 +290,7 @@
 The authoritative manual on Objective-C 2.0 is available from Apple:
 @itemize
 @item
-@uref{https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html}
+@uref{https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html}
 @end itemize
 
 For more information concerning the history of Objective-C that is