Patch Set 2: I would prefer that you didn't submit this

This now works on Mac :-) 

The FSAccessJava needs to be enhanced to support file mode and some minor cleanup is left.

The reason why OSGi failed to load the shared library in the previous version was that I had defined Bundle-RequiredExecutionEnvironment: J2SE-1.5 in the fragment containing the shared library without having defined that JRE in Eclipse ! I accidentally removed this entry since I moved all Java code to org.eclipse.jgit and all of a sudden loading the native library worked. This looks really odd ...

With Java bundles this is causing no problem, apparently PDE then falls back using the defined Java 6 environment.

As a next step we should decide on the platforms we want to support and how to build the native code (I have no recent experience on that).