Changes

Changes from Mercurial (hg http://isabelle.in.tum.de/repos/isabelle/ default)

Summary

1. support for base64 via Isabelle/Scala/ML;
2. compile;
3. clarified signature: avoid overlap of String vs. Bytes (both are CharSequence);
4. clarified signature (again);
5. merged
6. clarified signature;
7. unused;
8. unused;
9. clarified signature: more structured arguments, notably for remote provers;
10. clarified signature;
11. clarified signature: avoid tmp file;
12. clarified signature for Scala functions;
13. clarified message output: flush already happens in write_message_yxml (see Isabelle/22b5ecb53dd9);
14. tuned;
15. clarified cache;
16. clarified signature: Bytes extends CharSequence already (see d201996f72a8);
17. clarified exceptions;
18. more uniform use of Byte_Message; support protocol_message with multiple chunks;
19. tuned signature;
20. tuned signature;
21. more robust treatment of empty markup: it allows to produce formal chunks;