- report an error if format is nil instead of crashing - treat '\f' like '\n' ('\f' has special meaning in the   tabwriter now)
- report an error if format is nil instead of crashing
- treat '\f' like '\n' ('\f' has special meaning in the
  tabwriter now)

R=rsc
DELTA=7  (4 added, 0 deleted, 3 changed)
OCL=29790
CL=29893

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go