Reworked the source so it will compile and run under glibc 2.0.7

and linux kernel 2.0.36 (though the dubious reasons why someone
would want to do that defy imagination ;)
 -Erik

tail.c

@@ -27,6 +27,7 @@
 #include "internal.h"
 
 #include <stdio.h>
+#include <stdarg.h>
 #include <assert.h>
 #include <errno.h>
 #include <sys/types.h>