This separates the concerns of "deserialization the AST structures" from
"reading and accessing a module file".
No functionality change.
Swift SVN r7338
This currently does a little dance to handle PolymorphicFunctionTypes.
These are currently implemented by referencing the GenericParamList of
an actual polymorphic function, so they can't be deserialized without
knowing which function they are attached to. To solve this,
PolymorphicFunctionTypes are serialized as regular FunctionTypes. Then,
when a generic function decl is being deserialized, it will rebuild
a PolymorphicFunctionType from the serialized type and its own generic
parameter list.
Requirements on the generic types are coming next.
Swift SVN r5983
These are implementing using trailing TUPLE_TYPE_ELT records after the
initial TUPLE_TYPE record. This is the next step towards function decls.
Element initializers are silently ignored for now.
Also, do serialize a record for IdentifierTypes, even though we're not
including the components yet, so that we don't serialize the underlying
type more than once.
Swift SVN r5683
