First, on x86-64 Linux does not reserve lower 2 Gb of the address space,
and a space saving trick in the runtime did not work properly, confusing
pointers and failure generation numbers together.
Second, we ignored protocol conformances inside the executable (only
considered shared libraries).
Swift SVN r25972
This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
