- packaging, .deb: switch from java6-runtime to java6-runtime-headless as we...

- packaging, .deb: switch from java6-runtime to java6-runtime-headless as we do neither need GUI nor WebStart

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@1520 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534