Link F<README> to the specially-processed README page
Use the TOC data to determine what we found during this batch

… instead of what the search subclass (RT::Pod::Search) found.

This ensures that ->found() returns true for the README and any
(old-style) UPGRADING-* files which are manually processed in
rt-static-docs itself but still recorded in the TOC.
Merge branch '4.0/link-readme-in-docs' into 4.0-trunk