make the core::ffi::va_list module private

the types are exported from `core::ffi` itself

library/core/src/ffi/mod.rs

@@ -23,6 +23,7 @@
 #[stable(feature = "c_str_module", since = "1.88.0")]
 pub mod c_str;
 
+mod va_list;
 #[unstable(
     feature = "c_variadic",
     issue = "44930",
@@ -30,13 +31,6 @@
 )]
 pub use self::va_list::{VaArgSafe, VaList};
 
-#[unstable(
-    feature = "c_variadic",
-    issue = "44930",
-    reason = "the `c_variadic` feature has not been properly tested on all supported platforms"
-)]
-pub mod va_list;
-
 mod primitives;
 #[stable(feature = "core_ffi_c", since = "1.64.0")]
 pub use self::primitives::{

library/core/src/ffi/va_list.rs

@@ -2,6 +2,12 @@
 //!
 //! Better known as "varargs".
 
+#![unstable(
+    feature = "c_variadic",
+    issue = "44930",
+    reason = "the `c_variadic` feature has not been properly tested on all supported platforms"
+)]
+
 #[cfg(not(target_arch = "xtensa"))]
 use crate::ffi::c_void;
 use crate::fmt;

library/core/src/intrinsics/mod.rs

@@ -53,7 +53,7 @@
     issue = "none"
 )]
 
-use crate::ffi::va_list::{VaArgSafe, VaList};
+use crate::ffi::{VaArgSafe, VaList};
 use crate::marker::{ConstParamTy, DiscriminantKind, PointeeSized, Tuple};
 use crate::{mem, ptr};