The memcheck/tests/sigprocmask test is designed to test that we handle

The memcheck/tests/sigprocmask test is designed to test that we handle
the old style sigprocmask system call correctly without corrupting
memory when we copy out the new (larger) signal mask into the user
provided old (smaller) signal mask.

It therefore makes no sense to run it on amd64 or any other platform
which only has the newer rt_sigprocmask system call, and indeed it
wasn't working because we weren't passing the extra argument which
that call expects.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4990