Add support for interpreter directives in Bird tracks.
Add support for interpreter directives in Bird tracks.

phadej/stack,sjakobi/stack,Blaisorblade/stack,Fuuzetsu/stack,deech/stack,AndrewRademacher/stack,MichielDerhaeg/stack,martin-kolinek/stack,anton-dessiatov/stack,Heather/stack,Blaisorblade/stack,deech/stack,AndreasPK/stack,Heather/stack,Fuuzetsu/stack,AndreasPK/stack,sjakobi/stack,phadej/stack,mrkkrp/stack,mrkkrp/stack,AndrewRademacher/stack,martin-kolinek/stack,juhp/stack,anton-dessiatov/stack,juhp/stack,MichielDerhaeg/stack