Allow menu() to scroll.
Allow menu() to scroll.

This adds handling to the menu function such that we
can scroll up/down when the screen is longer than the number
of choices.

We also add key-handling for:

* HOME
* PAGE_UP
* PAGE_DOWN
* TAB.

This updates  #74.

skx/kilua,skx/kilua,skx/kilua,skx/kilua