Recent changes.

[Ulf Ekström]

Hi All. I have checked in a number of changes into the CVS.
We now have an "interactive" shell, which can be used to
modify the game in place. Hit F1 during play to halt the
game and go into shell mode.Type "help" into the shell to
get some tips on the syntax. Currently only level 0 has been
converted to the new format, I can do the rest in a little while.

One point of the new language is that it's extremely simple to
extend the shell. Write a C function

int my_shell_fun(int argc, char *argv[])
{
  blah blah
  shell_print("blah blah")
  return 0;
}

And do

shell_defun("blah",my_shell_fun) to make it available in the shell.

With this I hope we can speed up development again.

Regards,
Ulf