wrappers: Use C casts for polymorphic types.
wrappers: Use C casts for polymorphic types.

It looks like C++ casts end up being too restrictive, with different
casts causing different compilation errors.

joshua5201/apitrace,joshua5201/apitrace,tuanthng/apitrace,EoD/apitrace,schulmar/apitrace,EoD/apitrace,surround-io/apitrace,apitrace/apitrace,swq0553/apitrace,trtt/apitrace,apitrace/apitrace,trtt/apitrace,tuanthng/apitrace,apitrace/apitrace,tuanthng/apitrace,joshua5201/apitrace,apitrace/apitrace,schulmar/apitrace,EoD/apitrace,joshua5201/apitrace,swq0553/apitrace,schulmar/apitrace,trtt/apitrace,surround-io/apitrace,schulmar/apitrace,surround-io/apitrace,joshua5201/apitrace,EoD/apitrace,surround-io/apitrace,swq0553/apitrace,swq0553/apitrace,trtt/apitrace,trtt/apitrace,tuanthng/apitrace,swq0553/apitrace,tuanthng/apitrace,EoD/apitrace,surround-io/apitrace,schulmar/apitrace