Enable libgcj for Linux targets

[Bryce McKinlay]

Now that the V3 ABI is supported by Java, libgcj should build and work
out-of-the-box on most linux platforms, at least.

This patch removes libgcj from linux $noconfigdirs so that it will be
built by default when GCC is configured with
"--enable-languages=java,...". Hopefully this can also be done for other
platforms once some build portability issues are resolved.

ok to commit?

regards

  [ bryce ]