vlc_timestamp_helper: fix compilation from C++ modules

include/vlc_timestamp_helper.h

@@ -43,10 +43,10 @@ typedef struct
 
 static inline timestamp_fifo_t *timestamp_FifoNew(uint32_t capacity)
 {
-    timestamp_fifo_t *fifo = calloc(1, sizeof(*fifo));
+    timestamp_fifo_t *fifo = (timestamp_fifo_t *)calloc(1, sizeof(*fifo));
     if (!fifo)
         return NULL;
-    fifo->buffer = vlc_alloc(capacity, sizeof(*fifo->buffer));
+    fifo->buffer = (vlc_tick_t*)vlc_alloc(capacity, sizeof(*fifo->buffer));
     if (!fifo->buffer) {
         free(fifo);
         return NULL;