The type of the argument to the storer(FileDescTy&) function has been
changed to an OIOofd&. and the argument to the
readFrom(FileDescTy&) function has been changed to an OIOifd&.
OIOifd and OIOofd are not abstract classes, and their I/O
operators are not virtual functions as in OIOin and OIOout, so
using them does not incur the overhead of a virtual function call for each
member variable.