This makes it possible to avoid the misnamed prefix "bright". It is
misnamed because (on current terminal emulators, when the brightening
of bold is switched off) it just makes the typeface bold, not the color
brighter. The prefix "light" will now only make the color brigther,
and the modifier "bold" will just make the typeface bold (on terminal
emulators, when the brightening of bold is switched off).
On a Linux console, which is not capable of bolding the typeface,
"bold" will brighten the color.
This fully fulfills https://savannah.gnu.org/bugs/?58503.
c275c5158e