time output buffering

[Philip Rowlands]

time makes a lot of syscalls for a small amount of output, due to putc(3) 
writing to stderr.

Suggest that time calls setvbuf(stderr, NULL, _IOLBF, 0), specified in C89.


Cheers,
Phil

### Before
$ strace -e trace=write -c time true
0.00user 0.00system 0:00.01elapsed 0%CPU (0avgtext+0avgdata 472maxresident)k
0inputs+0outputs (0major+145minor)pagefaults 0swaps
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0       112           write
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                   112           total


### After
$ strace -e trace=write -c ./time true
0.00user 0.00system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 476maxresident)k
0inputs+0outputs (0major+147minor)pagefaults 0swaps
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         2           write
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                     2           total