Split out S_refcounted_he_new_common() from

Split out S_refcounted_he_new_common() from
Perl_refcounted_he_new_common(), so that Perl_store_cop_label() can
call it without needing to create two temporary SVs. Use it in
newSTATEOP() and eliminate the two temporary SVs. Make
Perl_fetch_cop_label() more defensive by not assuming that the value
for ":" is always a PV. Remove its "compatibility" macro.

p4raw-id: //depot/perl@33657