core: Add command-line option --defaultsupp

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14080 a5019735-40e9-0310-863c-91ae7b9d1cf9
drd/tests/std_thread2: Re-enable

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14081 a5019735-40e9-0310-863c-91ae7b9d1cf9