You can't have two mainpage items, and the second was just being
ignored. This restores them, which makes the left side list longer,
which we may or may not like, but it's at least how it was documented to
be.
Somewhat replaces some earlier work done by hg/lg, but much more
complete, so we kept it as is, because it's bringing in even more parts
after this.
Reviewed-by: Karl Palsson <karlp@tweak.net.au>
Applies to both, and clearly shows that cmu.h needs to be extracted as
common code.
Originally from: e31d312331
and checked in the HG/LG reference manuals.
