swift234

Teach dynamic lookup to find subscript operators.

The name used for name lookup of subscript operators is "__subscript",
but when looking into an Objective-C module we instead need to look
for methods with the subscripting selectors, e.g.,
objectAtIndexedSubscript:/objectForKeyedSubscript:. Do so, and make
sure that deserializing the method first still creates the subscript
declaration.

Fixes the majority of <rdar://problem/14656624>. We can subscript 'id' now.



Swift SVN r8700