Updated numeric handling, and renamed peek/poke.

We needed to update the storing of integers, because the
following program failed:

        #
        # Set the byte at 0x5000 to read "NOP"
        #
        store #1, 0x50
        store #2, 0x5000
        poke #1, #2

        #
        # Set the byte at 0x5001 to read "EXIT"
        #
        store #1, 0
        store #2, 0x5001
        poke #1, #2

        #
        # Jump to that new code.
        #
        goto 0x5000

Now it works as expected.