Add listing 5-5 (filling the screen).
Add listing 5-8 (replacing a word).
Add listing 6-1 (clrtobot, clrtoeol).
Add listing 7-1 (nodelay).

This commit also overloads getch to accept a char& and return a bool
thus supporting effective use of nodelay while allowing the original
nullary getch to throw an error when NCurses returns ERR (as when
nodelay is set, getch is called, and no character is available).