BZ #80: Mauve java.lang.System.arraycopy crashes on powerpc with -O2

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It works with -O0, but it crashes with -O2.  It also depends on the GCC version, but I
think it's not a GCC bug.

builtin_arraycopy crashes for a length < 0, when it takes the exception path.  The
actual crash seems to be caused by an invalid return address.  To small stacksize in the
stub?

This one crashes:
gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

But this one works:
gcc version 4.0.4 20060904 (prerelease) (Debian 4.0.3-7)

I stepped through the program with GDB and it seems the failing function is not
builtin_arraycopy, but builtin_i2f:

(gdb) finish
Run till exit from #0  0x0fbc0c84 in builtin_i2f (a=<value optimized out>) at
builtin.c:1929
RunnerProcess:restart-timer

... and it hangs forever.  At least on my PowerBook G4.

I found the problem and it's in builtin_arraycopy.  The problem are the range checks
with corner-case values like:

      // Regression test for missing check in libgcj.
      harness.check (copy (x, 4, y, 4, Integer.MAX_VALUE),
                     "caught IndexOutOfBoundsException");

Our range checks were simply wrong (missing unsigned casts)!  I wonder why this was
possible for such a long time...

This changeset fixes the range checks and I also added a junit testcase so we have a
test even without running Mauve:

http://mips.complang.tuwien.ac.at/hg/cacao/rev/75bfed30df25