Commit: Gas: Add .nop directive.

[Maciej W. Rozycki]

On Mon, 14 Sep 2020, Nick Clifton via Binutils wrote:

>   Fact 1 is important as it allows the directive to be used to generate
>   architecture neutral test cases containing real instructions.

 Indeed, and I bet some of our test cases can be cleaned up to use the new 
pseudo-op now.  ISTR making such test cases myself.  Thanks for the idea 
and implementation.

  Maciej