Introduce where
Make clear that bounds are syntactic sugar
Update semantics for cases where no type parameters are involved
Change rule to forbid trivial where clauses; purge discussion of multidispatch pattern, as it now seems that multidispatch is frequent enough to merit better support.
Clarify that where clauses cannot yet appear on trait methods.
Merge remote-tracking branch 'nikomatsakis/where-clauses'
66 - Where clauses