[mkgmap-dev] Move to Java 1.8

Hi all, Java 1.7 is no longer maintained, so I guess that most users are already using Java 1.8 I'd like to change the build of splitter and mkgmap to use 1.8 instead of 1.7 soon, JOSM already requires 1.8. I needed a newer ant version, 1.8.4 did not work with JDK 1.8, but 1.9.7 seems to work fine. @Steve : I think we don't need a warning message for users with an older JRE, but I don't know if you need time to change the build environment? Gerd