- in places where direct reading from the std::stream is used,
  this method can be used to ensure that the OpenFOAM Sstream state
  is properly updated from the std::stream.

ENH: restrict stream renaming to ISstream

- non-const access was previously declared at the top-level (IOstream)
  but that not only added in potentially odd setting of the static
  fileName, but also meant that the OFstream name() could potentially
  be altered after opening a file and thus be inconsistent with the
  underlying file that had been opened.

  Now restrict name modification to ISstream (and ITstream
  counterpart). Does not affect any existing valid code.

STYLE: non-default OFstream destructor (for future file staging)