Strip unnecessary imports for packages with no modules.
Strip unnecessary imports for packages with no modules.

Note that even an empty package needs to define Package[name] = {}, so
that other packages can tell at runtime whether it's installed.

Fixes #7927.

mjmasn/meteor,mjmasn/meteor,mjmasn/meteor,mjmasn/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,mjmasn/meteor,Hansoft/meteor,mjmasn/meteor,mjmasn/meteor