Move storage of final vtbl from BaseClass to IrInterface: BaseClass instances are shared! Always use the target's irstruct interfaceMap when building the const initializer. Tango helloworld works again.

import tango.io.Console;
void main()
{
    Cout("getting name std").newline;
    Cerr("getting name err").newline;
    auto s = Cin.get();
    Cout("putting name").newline;
    Cout (s).newline;
}