avoid some old-style cast warnings * cdisplay.h, cdisplay.c: New files. Compile C code and headers with C compiler. * corefcn/module.mk: Include them in the appropriate lists. * display.cc (display_info::init): Call new octave_get_display_info function.

%!function r = f (x)
%!  if (ischar (x))
%!    r = x;
%!  else
%!    error ("expecting character string");
%!  endif
%!endfunction

%!assert (eval ("f 10;"), "10");