[petsc-dev] Scotch

[Jose E. Roman]

I have rewritten the Scotch interface so that it can be used again as a MatPartitioning object. I have done limited testing, so please let me know if problems arise.

The interface is really to PT-Scotch rather than serial Scotch.

Some comments regarding configure's download-scotch option:
- It will probably fail in batch environments since the program 'dummysizes' must be run before compiling
- Compilation requires lex & yacc, I don't know if these are tested by configure.

Jose