swapon: swaps with legacy version label are not supported

Reviewed-by: Benno Schulenberg <bensberg@justemail.net>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
swapon, swapheader, mkswap: move swap signature to header

Both swapon and mkswap need to know what is valid device signature, so
share the value.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
libsmartcols: remove ununsed assignment

Value stored to 'rc' is never read.

[Karel: but you should still check the value]

Reviewed-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
lib/timeutils: fix memory leak

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
lib/pager: use names when referring to standard file descriptors

Signed-off-by: Sami Kerola <kerolasa@iki.fi>