ls(1): actually restore proper behavior

Highlights:

• CLICOLOR in the environment should imply --color=auto to maintain compatibility with historical behavior
• -G should set CLICOLOR and imply --color=auto

The manpage has been updated to draw the connection between -G and --color;
the former is in-fact a sort of compromise between --color=always and
--color=auto, where we'll output color regardless of the environment lacking
CLICOLOR/COLORTERM assuming stdout is a tty.

X-MFC-With: r361318