Drawing ACS-mode boxes in the terminal with Ruby

VT100 included an alternate character set (ACS) that enabled box drawing within the terminal. Here's a script from StackOverflow to test support for ACS:

If your stack supports Unicode, some software may choose to instead draw boxes using Unicode's "box drawing" block.

Related reading:

• About the 'alternate linedrawing character set'
• Tmux borders displayed as x q instead of lines?
• ncurses' NCURSES_NO_UTF8_ACS