Completely rewrote split_tac. The old one failed in strange circumstances.
Completely rewrote split_tac. The old one failed in strange circumstances.

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle