os_types: fix unsigned typedefs for MacOS

This effectively reverts f8ce071e1040c766157d630d920d6165d35fe422 which was
probably broken by 6449883ccacfee276ed9d99fa047342cdc51ab88.
diff --git a/include/ogg/os_types.h b/include/ogg/os_types.h
index eb8a322..e655a1d 100644
--- a/include/ogg/os_types.h
+++ b/include/ogg/os_types.h
@@ -72,11 +72,11 @@
 
 #  include <sys/types.h>
    typedef int16_t ogg_int16_t;
-   typedef uint16_t ogg_uint16_t;
+   typedef u_int16_t ogg_uint16_t;
    typedef int32_t ogg_int32_t;
-   typedef uint32_t ogg_uint32_t;
+   typedef u_int32_t ogg_uint32_t;
    typedef int64_t ogg_int64_t;
-   typedef uint64_t ogg_uint64_t;
+   typedef u_int64_t ogg_uint64_t;
 
 #elif defined(__HAIKU__)