using archetypes so that, e.g., an archetype T that conforms to
Ordered can be compared with <. Requires the introduction of
'archetype' constraints, so that we don't run amok and allow the use
of operators in protocols for *any* type that meets the requirements
of the protocol. This may change later, with default implementations,
of course.
The egregious hack introduced in Char.isSpace() works around known,
massive performance problems with the solver's exploration of the
state space. In this case, we have 6 instances of ==, each of which
has 18 overloads, for a large state space. However, we compound the
problem significantly by trying many possibilities for the ~30 type
variables in each state, rather than concluding quickly (as we should)
that most of those branches don't make sense.
Swift SVN r2922
