tmpfiles: exclude /var/tmp/systemd-private-* too
man: mention that PrivateTmp means /var/tmp too
man: docbook consitency fixes

Use proper (or at least more proper) docbook tags for various
fields. This should help with automatic parsing of the documentation.
man: extend systemd.directives(7) to all manual pages

New sections are added: PAM options, crypttab options, commandline
options, miscellaneous. The last category will be used for all
untagged <varname> elements.

Commandline options sections is meant to be a developer tool: when
adding an option it is sometimes useful to be able to check if
similarly named options exist elsewhere.
make-directive-index: use original XML as index entries

udev(7) fields are now display in whole, which looks
much better.