libbb: shrink sump.c

libbb: shrink sump.c

function                                             old     new   delta
dot_flags_width_chars                                  -      16     +16
int_convs                                              -       7      +7
lcc                                                    7       -      -7
index_str                                             16       -     -16
rewrite                                             1013     937     -76
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 0/1 up/down: 23/-99)            Total: -76 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>