Fixed #8149 -- Fixed File.__iter__() to handle other newline types.

Fixed File to use universal newlines. The following are recognized as
ending a line: the Unix end-of-line convention '\n', the Windows
convention '\r\n', and the old Macintosh convention '\r'.
Shouldn't the line 112 also be adapted ? `chunks()` could have split the bytes between a `\r` and a `\n`, hence the following might lead to unexpected results:
```Python
if line[-1:] in (b'\n', b'\r'):
    yield line
```