doc: miscellaneous documentation improvements * aspell-octave.en.pws: Add new words to spelling dictionary. * expr.txi: Use hyphens in "element-by-element" construction. * install.txi: Miscellaneous docstring improvements. * mk_undocumented_list: Update script. * xlim.m: Add ylim and zlim to function index. * data.cc: Add inf and nan to to function index. * file-io.cc: Add octave_tmp_file_name to function index. Expand docstring for SEEK_CUR and SEEK_END. * help.cc: Miscellaneous docstring improvements. * syscalls.cc: Improve docstrings for F_XXXX series of functions.

#include <octave/oct.h>

DEFUN_DLD (helloworld, args, nargout,
  "Hello World Help String")
{
  int nargin = args.length ();
  octave_stdout << "Hello World has " << nargin
        << " input arguments and "
        << nargout << " output arguments.\n";
  return octave_value_list ();
}