swift234

IRGen: Build field type vector accessor functions.

As part of the nominal type descriptor for a struct or class, build a function that lazily generates the vector of type metadata for the fields of the nominal type given an instantiation of the type's metadata. To cache this for nongeneric types, produce a global variable we can stash the result in, or for generic types, reserve some space in the metadata template so that generic metadata instantiation naturally provides a space for every instance of the type.

Reapplying now that the missing Float80 builtin metadata is available.

Swift SVN r15260