Changes

Summary

1. tuned;
2. more markup; multiple error output;
3. added document antiquotation @{session name}; renamed protocol function "Prover.session_base" to "Prover.init_session_base" according to the ML/Scala operation;
4. more accurate parse_nat/parse_int: avoid corner cases of Int.fromString (e.g. "1.0");
5. tuned;
6. disallow theory name "ROOT";
7. PIDE markup for session ROOT files;
8. tuned;
9. more operations;
10. tuned;
11. recovered Options.default_markup, e.g. for src/Doc/antiquote_setup.ML (amending 16519cd83ed4);
12. tuned;
13. clarified signature;
14. clarified signature;