Add EPOLLRDHUP constant

libc/sysdeps/linux/common/sys/epoll.h

@@ -45,6 +45,8 @@ enum EPOLL_EVENTS
 #define EPOLLERR EPOLLERR
     EPOLLHUP = 0x010,
 #define EPOLLHUP EPOLLHUP
+    EPOLLRDHUP = 0x2000,
+#define EPOLLRDHUP EPOLLRDHUP
     EPOLLONESHOT = (1 << 30),
 #define EPOLLONESHOT EPOLLONESHOT
     EPOLLET = (1 << 31)