[Mesa-dev] i965 Gen4/5: Garbage rendering when gl_BackColor is written but gl_FrontColor is not

[Chris Forbes]

I think I'd prefer to have the VS enable the other slot, and write a
constant (black or white?) into it.
Copying from one to the other in two-sided mode reduces the value of
the tests too much for my liking.

Having read the rest of the series more carefully now, I can see it's
all machinery I was about to have to reinvent anyway, so doubly-keen
to tidy it up now.

-- Chris