Read typedef and "using" type alias declarations and serialize into the
internal structures. Emit this information in the YAML output. The HTML
and MD generators are unchanged.
Separate out the logic to create the parent namespace or record object
and insert the newly created child into it. This logic was previously
duplicated for every "info" type and is now shared.
To help this, a struct containing the child vectors was separated out so
children can be added generically and without having too many templates.
A small change was made to populateParentNamespaces() to allow using
types that aren't themselves DeclContexts (typedefs are the first
example of this).
Differential Revision: https://reviews.llvm.org/D134371
21fb70c6ab