[GRASS-dev] r51975, vlib: improve PostGIS topology support, introduce level 3

[Markus Metz]

Hi Martin,

I find the newly introduced level 3 for topology confusing because 1)
level 3 could sometime in the future mean 3D topology, 2) level 3
applies only to PostGIS. Before that change, the open level had the
same meaning independent of the vector format (GRASS, PGR, PostGIS).
The open level is important for modules, and for modules it does not
matter if topology is pseudo-topology or PostGIS topology or true
GRASS topology. Modules only check if topology is available or not,
but are and should not be interested in what kind of topology is
available. This should be handled by the vector libs. I would
therefore prefer to keep the two open levels and rather have a flag in
struct Format_info_pg indicating whether this map is opened with
pseudo-topology or PostGIS topology.

Markus M