Add strnlen on platforms that don't have it, such as OS X

strutil.c

@@ -27,6 +27,15 @@
 
 static int xvsnprintf(char *str, size_t size, const char *format, va_list ap);
 
+/* Add strnlen on platforms that don't have it, like OS X */
+#ifndef strnlen
+size_t
+strnlen(const char *s, size_t n)
+{
+	const char *end = (const char *) memchr(s, '\0', n);
+	return(end ? end - s : n);
+}
+#endif
 
 static int
 xvsnprintf(char *str, size_t size, const char *format, va_list ap)