man: run dbus api docs through the updater

This replaces the api export tables with updated versions, and inserts
comments for all "undocumented" items. The slow work of documented them
is left for later ;)

lxml does some formatting changes that are not significant for lxml processing,
but generate spurious difference in the diff (namely: ulinks become one-line,
and double quotes are used instead of single quotes for element attribute
values). This should be a one-time thing: subsequent renegeration should be
idempotent with regards to this.