bench: fix compilation on hurd

Patch by Samuel Thibault.

https://github.com/xkbcommon/libxkbcommon/issues/39

Signed-off-by: Ran Benita <ran234@gmail.com>

bench/bench.c

@@ -35,6 +35,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 #include <stdio.h>
 

bench/bench.h

@@ -25,6 +25,8 @@
 #ifndef LIBXKBCOMMON_BENCH_H
 #define LIBXKBCOMMON_BENCH_H
 
+#include <stdint.h>
+
 struct bench_time {
     long seconds;
     long milliseconds;