docs: upadte v2.23-ReleaseNotes

Signed-off-by: Karel Zak <kzak@redhat.com>
build-sys: keep libuser optional

Signed-off-by: Karel Zak <kzak@redhat.com>
build-sys: release++ (v2.23-rc1)

Signed-off-by: Karel Zak <kzak@redhat.com>
libmount: umount crashes when trying to umount a non-mountpoint

Reported-by: Mantas Mikulėnas <grawity@gmail.com>
Signed-off-by: Karel Zak <kzak@redhat.com>