replace stdint.h with cstdint

The former is deprecated by C++14. The standard says they are the same:

The header defines all types and macros the same as the C standard library
header<stdint.h>.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/queue/Queue.hxx

@@ -26,10 +26,9 @@
 #include "util/LazyRandomEngine.hxx"
 
 #include <cassert>
+#include <cstdint>
 #include <utility>
 
-#include <stdint.h>
-
 class DetachedSong;
 
 /**

src/queue/QueuePrint.hxx

@@ -25,7 +25,7 @@
 #ifndef MPD_QUEUE_PRINT_HXX
 #define MPD_QUEUE_PRINT_HXX
 
-#include <stdint.h>
+#include <cstdint>
 
 struct Queue;
 class SongFilter;