Using C++ iostreams, rather than C FILE*’s.

Work arounds for a few bugs in p2c’s code generation (when StructFiles=0) were put in-place.
DVI output redirected to a std::ostream.
TeX file input may be passed in as a std::istream.
Removing pre-processor macros.

- I/O macros have been replaced with templated functions.
- A std::bitset has been substituted for the byte array + bit manipulation macros.