bug#34618: 26.1.92; timerfd interface causes slowdown on Cygwin

[Eli Zaretskii]

> From: Ken Brown <kbrown@cornell.edu>
> Date: Fri, 22 Feb 2019 15:08:33 +0000
> 
> Starting with cygwin-3.0.0, Cygwin has the timerfd functions.  But using
> them causes Emacs to be very slow to respond to user input.  If I press
> a key, there is a 1-2 second delay before Emacs responds.  I'm in the
> process of trying to debug this
> (http://www.cygwin.org/ml/cygwin/2019-02/msg00364.html).  In the
> meantime, the attached patch disables the use of these functions.
> 
> OK for the emacs-26 branch (after filling in the bug number)?

Yes, thanks.