swift234

When looking for conformances, make sure to check inherited conformances too.

Previously, if we were looking for, say, ForwardIndex conformance on Int,
we would see that Int is a BidirectionalIndex, and that BidirectionalIndex
refines ForwardIndex...but we'd have no way to get a conformance from
BidirectionalIndex (since it's not really BidirectionalIndex that conforms
to ForwardIndex, but rather Int-via-BidirectionalIndex). Change
Module::lookupConformance's helper findExplicitConformance to actually keep
conformance records around and walk those instead of just looking at the
ProtocolDecl's list of adopted protocols.

I don't have a minimal test case for this, but it fixes
<rdar://problem/15691181>, which allows DictionaryIndex to just adopt
BidirectionalIndex and have the ForwardIndex part be inferred. The problem
manifested as a crash in test/stdlib/Dictionary.swift, which just uses a
Dictionary in very basic ways, so I imagine we'll notice if this regresses.

Swift SVN r11521