[petsc-dev] uninformative docs for DMPlexGetStratumIS and DMPlexGetStratumSize

[Geoffrey Irving]

The documentation for DMPlexGetStratumIS helpfully explains that the
"value" argument is

    - value - The stratum value

One has to look in DMPlexStratify to find that the value is probably
(the word "value" isn't actually used) either the dimension or the
codimension.  But not which!

The documentation for DMPlexStratify seems to imply that the meaning
of the stratum value is up to the user.  Is that right?  If so it
makes it hard to design robust libraries; the library would have to
either know how the DMPlex was created or reverse engineer the
dimension 0 stratum from the coordinate section (or similar
hideousness).

If there is a convention, can I add it to the documentation of
DMPlexGetStratumIS and DMPlexGetStratumSize?

Geoffrey