swift234

Teach SILGen to only emit witness tables for conformances ascribed to the type declaration.

SILGen was emitting *all* of the witness tables associated with a type
along with the type definition, rather than just those conformances
that the type checker ascribed to the nominal type declaration
itself. Fixes rdar://problem/17489254 and rdar://problem/18448811.

Swift SVN r30167