Add some missing includes.

Change-Id: Ieec623c06bc32ec78334f628af25b00c2bccd2e7
diff --git a/libc/netbsd/gethnamaddr.c b/libc/netbsd/gethnamaddr.c
index 3ebe53e..728801f 100644
--- a/libc/netbsd/gethnamaddr.c
+++ b/libc/netbsd/gethnamaddr.c
@@ -67,6 +67,7 @@
 #include <netdb.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <strings.h>
 #include <syslog.h>
 
 #ifndef LOG_AUTH