Since SIGWINCH is being defined with a value above the existing NSIG,
redefine NSIG on WIN32.
PR-URL: https://github.com/libuv/libuv/pull/2032
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>