init: do not fail build if SIGPWR is not defined

Apparently, some *BSD variants (and maybe some other OSes) does not define
SIGPWR signal.  So since commit 760fc6debcba8c, busybox fails to build on
such platforms.  Fix this.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
uname: fix up usage documentation

The -i/-o options were missing, and the -r/-s/-v options were
incorrectly labeled as "OS" instead of "kernel".

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
appletlib: fix set-but-unused warning

When you build with FEATURE_INSTALLER disabled, you get a build
warning like so:

libbb/appletlib.c: In function 'busybox_main':
libbb/appletlib.c:691:7: warning: variable 'use_symbolic_links' set but
                                  not used [-Wunused-but-set-variable]
   int use_symbolic_links;
       ^

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
zcat: complain if input is not compressed

function                                             old     new   delta
buffer_fill_and_print                                178     191     +13
varvalue                                             735     743      +8
bbunpack                                             747     755      +8
open_zipped                                           85      89      +4
xmalloc_open_zipped_read_close                        61      63      +2
get_addr_1                                           240     242      +2
fbsplash_main                                       1228    1230      +2
pstree_main                                          322     321      -1
builtin_type                                         121     119      -2
do_load                                              954     926     -28
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 7/3 up/down: 39/-31)              Total: 8 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
catv: suppress compiler warning

The warning was:
warning: typedef 'BUG_const_mismatch' locally defined but not used [-Wunused-local-typedefs]

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
wget: fix use-after-free of ->user. Closes 6836

function                                             old     new   delta
wget_main                                           2207    2223     +16
parse_url                                            339     353     +14

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ifupdown: support 'link' address family

Does not configure anything. L2 configuration hook scripts should do
their job on receiving ADDRFAM=link. Configuration will be done only
once, irrespective of L3 protocols used.

Using the 'link' family in the interfaces file conforms to the Debian
implementation:

http://sources.debian.net/src/ifupdown/0.7.47.1/link.defn

function                                             old     new   delta
link_methods                                           -      12     +12
addr_link                                              -      12     +12
link_up_down                                           -       6      +6
static.addr_fams                                      12      16      +4
------------------------------------------------------------------------------
(add/remove: 3/0 grow/shrink: 1/0 up/down: 34/0)               Total: 34 bytes

Signed-off-by: Kaarle Ritvanen <kaarle.ritvanen@datakunkku.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
udhcpc: don't use BPF filter, users report problems (bugs 4598, 6746)

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
sendmail: make -f optional, document its default value

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