[CMake] FindXXX.cmake specification inconsistency

[r.koebler at yahoo.de]

> > should XXX_INCLUDE_DIRS and XXX_LIBRARIES *really* be excluded from
> > the (user-configurabe) cache?
> > (I don't think so, because then it's not possible for the user to
> >  configure these paths...)
> 
> The preferred method is for the user to set CMAKE_INCLUDE_PATH and
> CMAKE_LIBRARY_PATH appropriately, see
> http://www.cmake.org/Wiki/CMake_Useful_Variables. The advantage of this
> approach is it greatly reduces the number of different variables that the
> user has to worry about.
ok, so XXX_INCLUDE_DIRS and XXX_LIBRARIES should be in the cache, but
hidden/INTERNAL. right ?

(unfortunately, the FIND_* cannot create INTERNAL cache entries, so
 one has to make every FIND_*-variable INTERNAL by an extra SET-line...)

regards,
Roland