Changes

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

Summary

1. merged
2. tuned proofs --- avoid z3, which is absent on arm64-linux;
3. proper condition: z3 could be absent, e.g. on arm64-linux;
4. build auxiliary jEdit component in Isabelle/Scala; clarified directory layout;
5. separate component for idea-icons.jar, from jedit_build (see also ff0e0bb81597);
6. tuned message;
7. clarified signature;
8. tuned signature;