Commit 0b2841f9 introduced a workaround for a problem opening FIFOs with the 
O_PATH flag, in Cygwin versions 3.0.0 through 3.0.7.  It turns out that there 
are problems opening sockets and symlinks with O_PATH in versions 3.1.0 through 
3.1.2, so the workaround needs to be extended to these versions.

The attached patch does this.  The bug number still has to be filled in.

In GNU Emacs 27.0.60 (build 2, x86_64-pc-cygwin, GTK+ Version 3.22.28) of 2020-01-30
Repository revision: de411615344d1551d685e45b0739e1f738cf4afd
Repository branch: emacs-27