Merge branch 'tests-under-sanitizers'

* tests-under-sanitizers:
  test: fix memory leaks for https (add BEV_OPT_CLOSE_ON_FREE)
  test: "fix" (with a quirk) leak in ssl/bufferevent_wm (w/o defer callbacks)
  test: disable bufferevent/bufferevent_pair_release_lock under ASAN (too tricky)
  test: detect test failures if atexit handler calls _exit(!0) (sanitizers)
  Add LSAN suppressions (for OpenSSL temporary quirk)
  Add TSAN suppressions
  ci: run tests under sanitizers

Fixes: #955