Comment 3 for bug 331095

This patch makes the failures reproducible on Linux.

At least one failure is in line PatienceSequenceMatcher_new, which wants to allocate 'backpointers' proportional to the number of lines in b, which fails if b is empty. So the choices there seem to be:

 * leave backpointers as null if b is empty; any attempt to access it will crash fairly obviously but we must cope if it's null when freeing it
 * allocate at least one byte (a bit gross) so that every platform works like gnu libc