curses fix: map our normal color pairs into the 0-7 range instead of 1-8,

curses fix: map our normal color pairs into the 0-7 range instead of 1-8,
in order to make our pairs fit on terminals such as dtterm where COLOR_PAIRS=8.
map the white/blue color pair onto 8 instead of 9, but only if that slot
is available; fall back on white/black otherwise.

it seems there may be an off-by-one error in the color pair manpages for
the various curses packages (?) if not, our 0 entry is unusable, but that's
the DIM_BLACK color and we don't use it anyway.