[Xr] Can the xrs argument be removed?

[Keith Packard]

Around 18 o'clock on May 22, Bill Spitzak wrote:

> My problem is not with this extra argument, but in getting the value of this 
> extra argument from deep inside a number of nested calls in some existing 
> software that was not written to pass this extra argument down.

The application can easily use a global variable for this; threaded apps 
can use TLS while non-threaded apps needn't even bother with that.  
Someone has to have global state to manage this, it's not clear the 
library needs to pander to such.

I'm more intrigued by the idea that we can eliminate visual clutter by 
getting rid of these extra arguments everywhere; that's an appealing 
aspect of the GL API.

-keith