rm special case for ty_struct from take glue

This is incorrect, as take glue isn't used for moves.
stop zeroing the drop flag in drop glue

this is only going to cover up real bugs, as it's not part of the model
used to prevent multiple destructor calls
auto merge of #9751 : thestinger/rust/immediate, r=alexcrichton

This is incorrect, as take glue isn't used for moves.