remove (mk)swap(on)

they idled in KEEP to be immediately usable on a certain aboriginal
release that lacked them.
since aboriginal re-added those commands, we can now abandon them.
add own su implementation

it turned out that busybox' su pulled in a lot of code from different
TUs, so it cannot easily be said if its attackable or not.
thus i implemented my own minimal su. it's been proof-read twice
by dalias, (and much more often by me) so it should be safe.
but feel free to study it as well and report any bug you see.

it's maintained separately in my "hardcore-utils" repo, but copied
into KEEP for simplicity.

solves half of #99
closes #32
busybox: don't build standalone su
bump attr
libcap2: remove hardcoded bash assumption
busybox: restore ping's ipv6 support
busybox: fix typo
busybox: fix sed expression stolen from musl's configure
kernel: add magic option which makes ext4 usable

closes #101
kernel: enable security flags which make setcap usable

closes #102
write-hd-image.sh: use ext4 for rootfs
add "ping-perms" package for enabling cap_net_raw on ping binary

closes #93
finalizes #32
core: add su and ping-perms
add posix-man to core
*-man: depend on less

since we tuned busybox' man to use less -s to display man pages,
we need the less package as well since bb doesnt implement the -s
switch:

-s or --squeeze-blank-lines
Causes consecutive blank lines to be squeezed into a single blank line.
This is useful when viewing nroff output.
kbd: add de-latin1-nodeadkeys layout
bison: depends on m4
stage1: add kbd
add relro LDFLAGS to butch defaults

this should give additional security (at least for dynamically
linked apps).
since the musl dynlinker does only non-lazy relocation anyway,
the "full" protection may be unnecessary, but one can never have
enough security...

http://tk-blog.blogspot.ch/2009/02/relro-not-so-well-known-memory.html
http://isisblogs.poly.edu/2011/06/01/relro-relocation-read-only/
dropbear: build with scp binary

in the same turn, use user-supplied cflags and install into bin
rather than into sbin.