Update libestr to 0.1.9.

0.1.9
- bugfix: invalid number string when creating string from integer

0.1.8
- bugfix: previous fix for string comparisons did not work properly

0.1.7
- bugfix: invalid comparison results for different-length strings

0.1.6
- bugfix: ascii hex code escapes did not work
Update rsyslog7 to 7.4.7.

Many bugfixes since 7.4.4, see release notes:

http://www.rsyslog.com/changelog-for-7-4-7-v7-stable/
http://www.rsyslog.com/changelog-for-7-4-6-v7-stable/
http://www.rsyslog.com/changelog-for-7-4-5-v7-stable/