Patch by Ron Adam to make repr(str8(...)) return something looking like

s'...' instead of '...', allowing it to be distinguished from unicode
strings.  This doesn't roundtrip -- for now, that's intentional, as the
goal is to rip these out rather than to make it a feature, and making
them stand out (breaking 8 more tests) helps us track them down so we
can rip them out.