xdr_private.h needs sys/types.h for u_char

u_char is defined in sys/types.h, which doesn't appear to get
included, at least in my environments.

Signed-off-by: Keith Packard <keithp@keithp.com>

newlib/libc/xdr/xdr_private.h

@@ -27,6 +27,7 @@
 #include <stdarg.h>
 #include <stdint.h>
 #include <sys/param.h>
+#include <sys/types.h>
 
 /* avoid including stdio header here */
 #ifndef __VALIST