[cpp] Add explicit cast to CastCharStar

std/cpp/CastCharStar.hx

@@ -2,7 +2,7 @@ package cpp;
 
 abstract CastCharStar( RawPointer<Char> ) to(RawPointer<Char>)
 {
-   inline function new(s:String) this = untyped s.__s;
+   inline function new(s:String) this = cast untyped s.__s;
 
    @:from
    static public inline function fromString(s:String) return new CastCharStar(s);