Use %f, not %lf when formatting doubles

%f is correct; %lf is only needed with scanf.  Apparently, on some
old BSDs, %lf is deprecated.

Didn't we do this before?  Yes, we did.  But we only got the
instances of %lf, not more complicated things like %.5lf .  This
patch tries to get everything.

Based on a patch for 3894 by grarpamp.