Changes

Summary

1. some updates and clarification on Assumption.export_term;
2. new theorem has_integral_UN
3. updated to jdk-17.0.2+8;
4. used elapsed time instead of cpu time in Mirabelle because the latter contain cpu time of all threads
5. NEWS
6. added Mirabelle option "-y" for dry run
7. tuned garbage optimization
8. added cpu time (in ms) to Mirabelle run_action output
9. added Mirabelle option -r to randomize the goals before selection
10. A new lemma about inverse image
11. proper treatment of $let variables in symbol table in Sledgehammer
12. removed unconditional TPTP symbol declaration for undefined_bool in sledgehammer

Summary

1. Removal of a lemma (now in the libraries) and a few tweaks