Changed several pointers to istream (and ostream) to references in c++-only sections...

Changed several pointers to istream (and ostream) to references in c++-only sections of the skeleton.

Patched up a variety of expected errors caused by changing istream* to istream&.

Added a stray 'make' at line 545.  Oops.

Changed the buffer_state struct to store std::streambuf* instead of std::istream* for C++ mode.  Changed interfaces in FlexLexer.h to take std::istream& instead of *.  Backward compatibility temporarily broken.

Patched up backward compatibility with reasonable behavior in the presence of null pointers.

Re-added backward-compatible versions of the yyFlexLexer methods that take iostream pointers.  All tests passing.