This commit includes uv/posix.h in one #elif instead of four.
PR-URL: https://github.com/libuv/libuv/pull/2302
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>