basic java (JNI) calls into rrdtool

This code imported from the original work by David A. Neitz for rrdtool/java integration. See http://oss.oetiker.ch/rrdtool/pub/contrib/.

In order to build, you will need the librrd-dev package. i.e.

  sudo apt-get install librrd-dev

Make sure that JAVA_HOME environment variable is set, then in the java directory run make:

cd java
make