When following up discussion about bug 1335323, I stumbled across the
following paragraph in the manual:
When system definitions are loaded from @file{.asd} files,
a new scratch package is created for them to load into,
so that different systems do not overwrite each others operations.
The user may also wish to (and is recommended to)
include @code{defpackage} and @code{in-package} forms
in his system definition files, however,
so that they can be loaded manually if need be.
I believe that this is no longer accurate. Fare, you changed to loading
everything into ASDF-USER, didn't you?
Also, LOCATE-SYSTEM isn't documented at all. I see that it's exposed by
interface.lisp, but I'm not sure why it is. If exposed, I'd like to
document it, but it looks like an outsider should always use FIND-SYSTEM.