logread: eliminate usage of data/bss

logread: eliminate usage of data/bss
ifup: don't remove virtual iface prefixes (eth0:0)

function                                             old     new   delta
shbuf                                                  4       -      -4
SMrup                                                  6       -      -6
SMrdn                                                 12       -     -12
static.label_buf                                      20       4     -16
get_var                                              158     140     -18
------------------------------------------------------------------------------
(add/remove: 0/3 grow/shrink: 0/2 up/down: 0/-56)             Total: -56 bytes
   text    data     bss     dec     hex filename
 783501     962    9260  793723   c1c7b busybox_old
 783483     942    9244  793669   c1c45 busybox_unstripped