couple small API changes to petsc-dev

PetscViewerFileType merged into PetscFileMode PetscViewerASCIISetFilename/Type() changed to PetscViewerFileSetName/Mode() to match what is used for Binary viewer PetscBinaryOpen() now takes PetscFileMode as argument instead of int Matt, This will mess up your python bindings. Dinesh and Satish, The viewers for netcdf and hdf5 have not been tested with this change and probably won't compile. They need to be in a nightly build. Barry