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>