Changes

Summary

1. more informative session result;
2. simplified signature (despite 448325de6e4f);
3. clarified signature;
4. tuned;
5. more realistic PIDE build session;
6. more uniform options;
7. asynchronous send_stop operation;
8. more process arguments;
9. proper message text (see also fa62e095d8f1);
10. support PIDE option (inactive); misc tuning;
11. more explicit build_session args; support both command-line and PIDE version;
12. avoid compiler warning;
13. actually throw exception;
14. clarified result;
15. reset print_mode, e.g. relevant for saved heap;
16. clarified init (see also 32755e357a51, ac48def96b69);
17. restore output channels after shutdown, e.g. relevant for saved heap;
18. clarified signature;