Add repl on usage without commandline arguments.

This building of shared objects is getting unwieldly.
The fact that the dynamic array and linked list implementations are
    totally separate from the rest of the code is good. But the
    builtins and the evaluate and value and repl stuff is all really
    messy. The idea of te builtin as an external and the evaluate as
    an internal thing is good except that I need to expose the repl
    and tree stuff to the main program as well.