[PATCH] Linux: Define struct termios2 in <termios.h> under _GNU_SOURCE [BZ #10339]

[Florian Weimer]

* Adhemerval Zanella:

> This allows us to adjust the baud rates to non-standard values using termios
> interfaces without to resorting to add new headers and use a different API
> (ioctl).

How much symbol versioning will be required for this change?

> As Peter Anvin has indicated, he create a POC [1] with the aforementioned
> new interfaces.  It has not been rebased against master, more specially against
> my termios refactor to simplify the multiple architecture header definitions,
> but I intend to use as a base.

Reference [1] is still missing. 8-(

Thanks,
Florian