splitting out documentation (was: cmake circular dependency)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> openldap then uses soelim to generate its man pages, which pulls in groff.
Another solution may be to split out the documentation from the main package.
(Or maybe to pre-generate the documentation.)

I don't have examples at hand, but I seem to remember other cases where 
building the documentation pulled in heavyweight dependencies for fancy 
documentation-generation tools