augeas: security bump to version 1.8.1

augeas: security bump to version 1.8.1

Fixes CVE-2017-7555 - Augeas versions up to and including 1.8.0 are
vulnerable to heap-based buffer overflow due to improper handling of escaped
strings.  Attacker could send crafted strings that would cause the
application using augeas to copy past the end of a buffer, leading to a
crash or possible code execution.

[Peter: extend description]
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>