ftpd: EPSV and SIZE support. Tested to work on IPv6 too.

ftpd: EPSV and SIZE support. Tested to work on IPv6 too.
libbb: str2sockaddr shuld accept [IPv6] addr without port -
 wget 'ftp://[::1]/file' needs that to work.

function                                             old     new   delta
bind_for_passive_mode                                  -     129    +129
get_nport                                              -      30     +30
ftpd_main                                           1731    1760     +29
str2sockaddr                                         412     431     +19
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(add/remove: 2/0 grow/shrink: 2/0 up/down: 207/0)             Total: 207 bytes
   text    data     bss     dec     hex filename
 808568     476    7864  816908   c770c busybox_old
 808804     476    7864  817144   c77f8 busybox_unstripped