util/u_queue: make u_queue accessible to cpp

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/util/u_queue.h

@@ -38,6 +38,10 @@
 #include "util/list.h"
 #include "util/u_thread.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Job completion fence.
  * Put this into your job structure.
  */
@@ -106,4 +110,8 @@ util_queue_fence_is_signalled(struct util_queue_fence *fence)
    return fence->signalled != 0;
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif