Use --enable-sjlj-exceptions when configuring gcc so that exception handling

Use --enable-sjlj-exceptions when configuring gcc so that exception handling
  works for dynamicly linked executables.  Only tested so far on i386 with
  gcc 3.3.2.  But combined with the latest ldso updates, I can now get a
  dynamicly linked java helloworld app to run.
Add a config toggle for building gcj and libgcj.  The build runs fine
  through gcc-final but currently requires hand interventions to build
  gcc-target.  Again, only tested so far on i386.