swift234

Resilience expansion is not an IR-generation concept.

If a type has to be passed or returned resiliently, it
will necessarily be passed indirectly, which is already
represented in SILFunctionType.  There is no need to
represent this as a separate channel of information.

NFC. Also fixes a problem where the signature cache
for ExtraData::Block was writing past the end of an
array (but into the storage for an adjacent array
which was fortunately never used).

ExtraData should also disappear as a concept, but we're
still relying on that for existential protocol witnesses.

Swift SVN r21548