Clearify running testsuite as part of patch submission

[Roland McGrath]

> Seeing that many here are not aware of "make xcheck", we can keep the 
> status quo and advertize "make xcheck" - or we change something. What 
> about switching them? So, check includes all tests but xcheck only those 
> safe in general?

No, 'make check' is the standard target and everyone expects that it is
safe to run in constrained environments.

What we should do first is document all the details of the xcheck cases
we have today.  Then we can consider the issue further.


Thanks,
Roland