format errors

[Dave Love]

Looking at a recent snapshot, there are still many printf-type format
errors revealed by gcc -Wall.  (I think there are a few other
significant warnings with -Wall which don't appear with the default
gcc compilation flags, but I haven't looked closely.)

I'd suggest developing under -Wall and turning off specific warnings
(-Wno-paretheses?) if you think that's too noisy, and it would be
worth at least adding -Wformat to the standard flags.