FROM A SMALL block of seriously old, gnarled and twisted Semillon bush vines planted in the Franschhoek valley circa 1905, grapes for The Pilgrimage Semillon are in very short supply. Taken down the road to Duncan Spence’s Rickety Bridge estate, the fruit is entrusted to cellarmaster Donovan Ackerman and his team in coming up with a very limited edition, less than