split: let me join bikeshed painting frenzy :)

split: let me join bikeshed painting frenzy :)
this one should be able to handle huge files.
   text    data     bss     dec     hex filename
    664       4       0     668     29c busybox.t0/coreutils/split.o
    628       0       0     628     274 busybox.t1/coreutils/split.o
split_main                                           488     525     +37
suffix_len                                             4       -      -4
next_file                                             77       -     -77
(add/remove: 0/2 grow/shrink: 1/0 up/down: 37/-81)            Total: -44 bytes