C fix threaded decl. for my_curse
improve ea3b3ff0 t/C-COMPILED/template.pl: TODO passed only when passed
C: dynamic COP file and stash threaded

several core tests (not one of our so far) do a cv_undef, which clears
the CvROOT op, which is a COP. So all COP fields must be dynamic, even under threads.

tested with t/CORE/op/bproto.t