Fix a bug in version-satisfies, found by stassats,
when a component has a NIL version.
The :initform nil was added in asdf 2.27, so we must handle this case,
but reset-system still drops the version
so we must still check for slot-boundp.
Bump version to 3.1.0.6
Add test for previously fixed issue with version-satisfies.
Tweak message for warning in version-satisfies.
Bump version to 3.1.0.7