DJGPP specific fix for struct serial_ops in ser-go32.c

[Eli Zaretskii]

> Date: Mon, 11 Jan 2016 19:48:01 +0100
> From: Juan Manuel Guerrero <juan.guerrero@gmx.de>
> 
> This is a fix for the DJGPP port of gdb.
> I do not know when this has changed but the numbers of arguments passed to
> setparity of struct serial_ops no longer match the number of arguments of
> dos_noop.  The patch below fixes the issue providing a new dummy function.

Any objections, anyone?  The patch looks obviously correct to me, so
I'd like to commit it.

Thanks.