Stop using the padlist to refcount GVs. Instead use regular magic. This allows various modules, including B::Deparse, to safely peek into pads of (re)named subs (Closes RT#42725) (Goro Fuji).
Support perl >= 5.13.3 by using the new CvGV_set interface there (Closes RT#59558).
Stop using the deprecated PL_no_symref (Closes RT#57843).