[Xr] Can the xrs argument be removed?

[Keith Packard]

Around 14 o'clock on May 22, Bill Spitzak wrote:

> Well, I am extremely glad this was not dismissed immediately. So there is
> actually some possibility of this happening? I personally feel this is
> enormously important and would make Xr a very popular and standard
> interface, due to the ease of imbedding the calls into existing code.

One possibility is to have a 'default' state which would be referred to 
with NULL; that default state would use TLS.   Suitable macro magic could 
even remove the argument from the application.

We might want (instead) to have a per-thread 'current' state; this would 
allow more flexibility while also avoiding some of the startup issues.

-keith