first sort by manual section (1, 8, 6, 2, 3, ...),
then by manual tree (share, X11R6, local)
and only for ties prefer cat over man.
For example, this avoids that /usr/local/man/cat7/roff.0
overrides /usr/share/man/man7/roff.7.
Triggered by a question from Jan Stary <hans at stare dot cz>,
ok dcoppa@ bentley@ jca@ pascal@.

ok dcoppa@ phessler@ jasper@ landry@ rpointel@ giovanni@ ajacoutot@ henning@
no problem jmc@

manuals on demand by man(1), even though a few manuals may still have
formatting issues with mandoc, and a tiny fraction may still make
mandoc error out.
Also remove the .me and .ms _build rules: we don't support these
formats any longer, and don't have any such manuals in base.
OK deraadt@ sthen@

ok deraadt@

ok jmc@, no objections espie@

- update paths for 3{F,f,P,p}
ok espie millert steven

and matches "zcat" (as opposed to uncompress -c");
grammar tweak whilst here too;
ok millert

man(1) searches, as well as from the numerical sections list, as they do
not exist
- remove the {contrib,new,old} sections, as they point to directories
that do not exist
- make the X11 section an alias for the X11R6 section (instead of
pointing to a non-existent directory)
ok millert

remove it (updating it makes little sense);
ok millert

Treat foo.n as a -man page, not a -me doc