Rendering XML requires the generated config-*.xml files and the files in
directory 'out' and 'pre', but not 'tmp'. Directories 'etc' and 'src' are
also required, but they are constant, i.e. not changed by building examples.

Actually 'make html' does four different things:

1. Go sure ulink.xml and calc.xml are built.
2. Patch etc/ldp.dsl with paths to system style sheets.
   This is a mess. If it fails try

     locate docbook | grep '\.dsl$' | less

   and incorporate the results somehow.
3. etc/mkhtml.sh intro
4. etc/mkhtml.sh platform

Step 1. is superflous if a plain 'make' succeeded. If you want to render
non-functional examples a 'make html_deps' will do as many calculations
as possible.

Step 2. is required only once. An explicit 'make dsl' should do.

Steps 3. and 4. can be called manually. They expect config.xml to be a
symbolic link to the actual config-file. If config.xml does not exist
it is set to config-$(HOSTNAME).xml.

Recommended procedure is to first do a 'make html' on your primary system.

To build the examples from secondary systems you copy the architecture
specific directory, i.e. the tar file generated by 'make dist_out' to
the primary system. Then change the symbolic link 'config.xml' and render
only the platform.

   ln -fs config-host.domain.xml config.xml
   etc/mkhtml.sh platform
