Minor change to "info format"

Author:Dáin
Date:Wed Jul 20 11:36:04 2016
Id:2504
You can now use "%," in an "info ..." format string to toggle whether to use a
thousand separator in output:

  > info %,%P
  123,456
  > info %,%P%, -- %P
  123,456 -- 123456

Thanks to Imago for the idea.

- Dain