Fix "call to undeclared library function 'memcmp'" error with current clang.

diff -u -r ../nfs-utils-2.6.4/support/include/sockaddr.h ./support/include/sockaddr.h
--- ../nfs-utils-2.6.4/support/include/sockaddr.h	2023-11-17 17:32:39.000000000 +0000
+++ ./support/include/sockaddr.h	2024-06-18 09:41:32.777237803 +0000
@@ -26,6 +26,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <stdbool.h>
 #include <sys/socket.h>
 #include <netinet/in.h>