Summary
- proper treatment of startup errors, notably for Pure ROOT.ML;
- proper treatment of protocol exceptions and prover termination: avoid session.stop while saving image;
- merged
- Added tag Isabelle2020-RC4 for changeset 1f3d9a9dd42a
- more robust, notably wrt. interrupts;
- merged
- more NEWS;
- clarified messages: indicate termination explicitly;
- avoid vacous type variable, due to "potentially redundant" shyps in Thm.unconstrainT;
- Added tag Isabelle2020-RC3 for changeset 7fe1a344404a
- updated to current cygwin-20200323, after 3.1.4-1 from 19-Feb-2020;
- avoid jdk-11.0.6+10: it shows problem "S8217731: Font rendering and glyph spacing changed from jdk-8 to jdk-11" https://bugs.openjdk.java.net/browse/JDK-8217731 even though the changelog claims to have resolved this;
- clarified signature: more direct Isabelle_Process.EXIT;
- proper arguments of protocol function;