Precis

Copperbox revision 1461.

More work extracting module lists from Cabal files. The new CabalPrecis datatype is now looking inadequate for the task though. A client using the Precis.Cabal modules has to do an awful lot of post-processing to get a list of private and public modules. Although the old datatype from version 0.4.0 had problems - the construction code in the presence of conditions wasn't right - it's starting to look a better choice than the current revision.