swift234

Teach TypeMember constraints to suggest force unwrapping optionals, the same way
value member constraints do.

This fixes:
<rdar://problem/21662365> QoI: diagnostic for for-each over an optional sequence isn't great

before we'd produce:
t.swift:3:10: error: '[Int]?' does not have a member named 'Generator'
for x in array {
         ^

now we produce:

t.swift:3:10: error: value of optional type '[Int]?' not unwrapped; did you mean to use '!' or '?'?
for x in array {
         ^



Swift SVN r29902