IWYU: memset and strerror_r used in simple epoll server require string.h include.

External contribution by "José Dapena Paz" <jdapena@igalia.com> at
https://quiche-review.googlesource.com/c/quiche/+/10880.

I verified that the author has signed the CLA.

PiperOrigin-RevId: 419825266

epoll_server/simple_epoll_server.cc

diff --git a/epoll_server/simple_epoll_server.cc b/epoll_server/simple_epoll_server.cc
index 28c301e..0092bb1 100644
--- a/epoll_server/simple_epoll_server.cc
+++ b/epoll_server/simple_epoll_server.cc
@@ -4,8 +4,9 @@
 
 #include "epoll_server/simple_epoll_server.h"
 
-#include <errno.h>   // for errno and strerror_r
+#include <errno.h>   // for errno
 #include <stdlib.h>  // for abort
+#include <string.h>  // for strerror_r
 #include <unistd.h>  // For read, pipe, close and write.
 
 #include <algorithm>