gcc/ChangeLog:
* doc/standards.texi (Standards): Fix markup.
There is no formal written standard for Objective-C or Objective-C++@.
The authoritative manual on traditional Objective-C (1.0) is
``Object-Oriented Programming and the Objective-C Language'':
-@uref{https://gnustep.github.io/@/resources/@/documentation/@/ObjectivCBook.pdf
+@uref{https://gnustep.github.io/@/resources/@/documentation/@/ObjectivCBook.pdf}
is the original NeXTstep document.
The Objective-C exception and synchronization syntax (that is, the