We check evp.sigev_notify_thread_id only if evp->sigev_notify has
SIGEV_THREAD_ID set. But before checking we need to make sure accessing
evp->sigev_notify is valid.
Fix memcheck/tests/x86-linux/scalar.stderr.exp output.
We now produce separate warnings for the 3 different fields.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13837