Rename --defaultsupp into --default-suppressions as requested by Julian

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14090 a5019735-40e9-0310-863c-91ae7b9d1cf9
helgrind/tests/tc20_verifywrap: Port to glibc >= 2.18

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14091 a5019735-40e9-0310-863c-91ae7b9d1cf9