asyncio: repr(Task) now also contains the line number even if the coroutine is

asyncio: repr(Task) now also contains the line number even if the coroutine is
done: use the first line number of the code object instead of the current line
number of the generator frame.

The name of the coroutine is not enough because many coroutines may have the
same name. It's a common case in asyncio tests for example.