Ticket #3050: don't use bright colors as background ones.

Only following colors can be used in 16-color skins:
black, red, green, brown, blue, magenta, cyan, lightgray.

Following colors are replaced in 16-color skins:

white -> lightgray
yellow -> brown
brightgreen -> green

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3050_bg_colors'

* 3050_bg_colors:
  Ticket #3050: don't use bright colors as background ones.