Update to JNR (JRuby Native Extensions) 1.1.8

We are in the process of packaging Gradle for Fedora (http://fedoraproject.org) and we found an small issue with the JNR libraries. Fedora already has newer versions of those libraries, 1.1.8 to be precise, and the native sub-package doesn't build correctly.

This patch updates the dependencies and the Java code to use those newer versions.

Having this in the gradle code base would simplify the packaging effort in Fedora.

Hope this helps!