simplify: set exprop=false during containment checks
For issue #521 (closed), reported by Jacopo Binchi.
- spot/tl/simplify.cc: Here.
- tests/core/521.test: New test case.
- tests/Makefile.am: Add it.
- NEWS: Mention it.
- THANKS: Add Jacopo Binchi.
For issue #521 (closed), reported by Jacopo Binchi.