Merge branch 'tr/valgrind'

Let us use not just memgrind but other *grind debuggers.

* tr/valgrind:
  tests: notice valgrind error in test_must_fail
  tests --valgrind: provide a mode without --track-origins
  tests: parameterize --valgrind option
  t/README: --valgrind already implies -v

diff --cc t/test-lib-functions.sh
Simple merge