use class for reading lexer input * input.h, input.cc (octave_base_input_reader, octave_terminal_reader, octave_file_reader, octave_eval_string_reader): New classes. (octave_gets): Now a member function of octave_base_reader. (get_user_input): Delete function. Move actions to octave_terminal_reader::get_input and octave_eval_string_reader::get_input. function. Call from octave_file_reader::get_input. Don't check whether reading an eval string. (current_eval_string, get_input_from_eval_string): Delete global variables. (get_debug_input): Check CURR_LEXER->input_from_eval_string instead of global get_input_from_eval_string variable. Don't protect get_input_from_eval_string. * lex.h (octave_lexer::input_reader): New data member. (octave_lexer::octave_lexer (void)): Initialize it. (octave_lexer::octave_lexer (const std::string&), octave_lexer::octave_lexer (FILE *)): New constructors. * lex.h, lex.cc (octave_lexer::input_buffer::fill): New function. (octave_lexer::input_buffer::read): Delete. (octave_lexer::read): Rename from octave_read. Call reader to get input, and then hand it to the input_buffer instead of asking the input buffer to read input. Change all callers. (octave_lexer::input_source, octave_lexer::input_from_eval_string): New functions. Call octave_lexer::input_from_eval_string instead of using get_input_from_eval_string. * oct-parse.in.yy (octave_parser::octave_parser (FILE *), octave_parser::octave_parser (const std::string&)): New constructors. (parse_fcn_file): Pass FILE pointer to octave_parser constructor. (eval_string): Pass string to octave_parser constructor instead of setting global current_eval_string variable.

## The `oregonator'.
##
## Reference:
##
##   Oscillations in chemical systems.  IV.  Limit cycle behavior in a
##   model of a real chemical reaction. Richard J. Field and Richard
##   M. Noyes, The Journal of Chemical Physics, Volume 60 Number 5,
##   March 1974.

function dx = oregonator (x, t)

  dx = zeros (3, 1);

  dx(1) = 77.27*(x(2) - x(1)*x(2) + x(1) - 8.375e-06*x(1)^2);
  dx(2) = (x(3) - x(1)*x(2) - x(2)) / 77.27;
  dx(3) = 0.161*(x(1) - x(3));

end