[petsc-dev] questions on new include organization

[Barry Smith]

1)  Can we move the section data structures from vecimpl.h to isimpl.h? in preparation for its refactoring and why is PetscSectionCreate in section.c defined in src/vec/vec/impls/seq?   Can vsection.c be split in two with the only the "Vec" related routines kept in the Vec directory?

2) matimpl.h really needs vecimpl.h?  

#define __MATIMPL_H

#include <petscmat.h>
#include <petsc-private/petscimpl.h>
#include <petsc-private/vecimpl.h>

Doesn't seem to so I've removed the vecimpl.h and pushed

Seems there may be a few of these unneeded dependencies hanging around, I'll try to hunt them down.

   Barry