Adapt documentation to reality.
(1) The fc-cat usage message should reflect the
options accepted by the program.
(2) The fc-cat.1 manpage was fairly broken (unreadable).
fonts.cache-1 files (e.g. for grepping and validation of the mmap
codepath), as per James Cloos' request.
Remove done 'TODO' comment.
Updates for development release 2.3.90.