new theorems

incorporated constant chars into instantiation proof for enum; tuned proofs for properties on enum of chars; swapped theory dependency of Enum.thy and String.thy

close code theorems explicitly after preprocessing

tuned proofs;

further attempts to cope with large files via option jedit_text_overview_limit;

more detailed Prover IDE NEWS;

recovered explicit error message, which was lost in b8570ea1ce25;

removed dead code;

proper signatures;

tuned;