build system: fix non-portable sed constructs.

This includes proper line breaks for labels and closing braces,
and removing non-portable \n and \t in s/// functions.

Signed-off-by: Matthias Andree <matthias.andree@gmx.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
libarchive: open_zipped() does not need to check extensions for e.g. gzip

We only need to check for signature-less extensions,
currently only .lzma. The rest can be happily autodetected.

This fixes "zcat FILE_WITHOUT_GZ_EXT" case, among others.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
lineedit: fix trivial build failure

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
tail: adjust help/usage texts

Signed-off-by: Cristian Ionescu-Idbohrn <cristian.ionescu-idbohrn@axis.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
fakeidentd: simplify ndelay manipulations

function                                             old     new   delta
new_peer                                              91      79     -12
do_rd                                                197     152     -45

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
tar: tighten up pax header validity check

function                                             old     new   delta
get_header_tar                                      1785    1795     +10

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