Instead, introduce a new hasDependentMember() recursive property.
The only place that cares about this is associated type inference,
where I changed all existing hasTypeParameter() checks to instead
check (hasTypeParameter() || hasDependentMember()). We could
probably refine this over time and remove some of the
hasTypeParameter() checks, but I'm being conservative for now.
Fixes <https://bugs.swift.org/browse/SR-4575> and
<rdar://problem/31603113>.
