Specify the type in pthread initializers as well.

Otherwise it would be possible to do e.g.

`pthread_mutex_t mutex = PTHREAD_ONCE_INITIALIZER;```,
which would expand to
```pthread_mutex_t mutex = {0};```.

src/header/bits_pthread/cbindgen.toml

@@ -5,10 +5,10 @@ style = "type"
 no_includes = true
 cpp_compat = true
 trailer = """
-#define PTHREAD_COND_INITIALIZER {0}
-#define PTHREAD_MUTEX_INITIALIZER {0}
-#define PTHREAD_ONCE_INIT {0}
-#define PTHREAD_RWLOCK_INITIALIZER {0}
+#define PTHREAD_COND_INITIALIZER ((pthread_cond_t){0})
+#define PTHREAD_MUTEX_INITIALIZER ((pthread_mutex_t){0})
+#define PTHREAD_ONCE_INIT ((pthread_once_t){0})
+#define PTHREAD_RWLOCK_INITIALIZER ((pthread_rwlock_t){0})
 """
 
 [export.rename]