Minor tweaks to Thread.xs. Integrate from ansi branch to mainline. Fix up ansiperl integration. Back to passing all expected tests with usethreads. Untested with non-threaded perl.
All tests now pass again for non-threaded perl.
Add per-interp thrsv to hold SV struct thread for main thread. Various fixes to Thread.xs. Started rewriting thread state machine. Still not completely done. Add methods self, equal, flags, list to Thread.xs.