couple small API changes to petsc-dev

[Barry Smith]

  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