Apply visibility to RawBuffer

Cargo.toml

@@ -6,3 +6,4 @@ members = [
     "vulkan-sys",
     "library_loader",
 ]
+resolver = "2"

vulkan-rs/src/memory.rs

@@ -12,7 +12,7 @@ impl_reprc!(
     #[derive(Debug, Copy)]
     pub struct RawBuffer {
         #[assume_reprc]
-        d: u8,
+        pub d: u8,
     }
 );