remove_unnecessary_notes breaks libjava build

[Richard Kenner]

    The errors I was getting was duplicate .LBB0/.LBE0 labels.  And the
    reason for that was that final_scan_insn was calling
    ASM_OUTPUT_INTERNAL_LABEL on NOTE_INSN_BLOCK_BEG and
    NOTE_INSN_BLOCK_END insns that did not have BLOCK_NUMBER (NOTE_BLOCK
    (insn)).  And the reason for that was that they had been skipped by
    renumber_blocks.  And the reason for that was BLOCK_DEAD had been set
    on the block in remove_unnecessary_notes, in the afore-mentioned
    patch.

But the only time BLOCK_DEAD is set is when the notes are deleted, so I'm
confused.  Can you look a bit more into this?

    The quick work-around is basically disabling the patch:

Which will cause the abort in function.c to be hit.