defined_cv: Skip saving defined(&cv) subs (#96)

Enable t/issue96.t
Add helper functions from oldmaster: svop_name, padop_name
use global curcv for pads
add GV::save filters, e.g. 8: do not save CV
added nextcop arg to method_named to get proper location info on -DC
t/testc.sh: add 2900 for issue 29 (B::C open utf8)