udhcpc: fix a problem with binary-encoded options #2

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

function                                             old     new   delta
attach_option                                        416     413      -3
allocate_tempopt_if_needed                            74       -     -74

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Merge git://busybox.net/busybox