Allow options blocks to override unseen module-sets.

In other words, we separate parsing of options blocks from whether
existing modules or module-sets have already been seen. Instead we
decide later (when expanding module-sets or modules) whether there are
any relevant options blocks to apply (this is the 'deferred option'
handling).

Now you should be able to declare options blocks that contain options
appropriate for module-sets, even if no module-set is defined with that
name (e.g. if you're doing weirdness with 'include' declarations).

This does require that you don't use the same name for modules and for
module-sets, but that is essentially already a requirement anyways.
There's no good way to always disambiguate that.

BUG:366594
FIXED-IN:16.10