=for apidoc Am|void|SvSetSV|SV* dsv|SV* ssv
Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
-more than once.
+more than once. Does not handle 'set' magic on the destination SV.
=for apidoc Am|void|SvSetSV_nosteal|SV* dsv|SV* ssv
Calls a non-destructive version of C<sv_setsv> if dsv is not the same as