[asdf-devel] Small testing convenience pushed

[Robert P. Goldman]

If you test on ACL with the many variations that Dave set up (thanks,
Dave!), there is a new problem: you end up testing upgrade over and over
and over and over, and it takes forever.

This recent commit adds the ability to set ASDF_TEST_UPGRADE_LISPS,
typically as a subset of ASDF_TEST_LISPS.  If the variable is unset, it
should not affect you (but this is not tested).

Best,
r