Comment 2 for bug 1579980

My thought was that, since the possible set of package options is defined to be open-ended, the sensible thing to do would be to replace `ecase` with `case`.

Alternatively, since ASDF uses `read` to snarf the package form, you could rebind `*features*` to add something specific and require any extended package options to be prefixed with a negative reader conditional. Then you would write something like:

    #-asdf-standard-package-options (:lock t)