boring: Suppress Clippy warnings about missing safety docs

I'm not quite sure why these are unsafe traits, probably to prevent
implementing them for random types accidentally. However, Clippy
demands a "# Safety" section in their docs. Tell it to get lost.

Author: ilammy

boring/src/pkey.rs

@@ -93,20 +93,23 @@ impl Id {
 }
 
 /// A trait indicating that a key has parameters.
+#[allow(clippy::missing_safety_doc)]
 pub unsafe trait HasParams {}
 
 unsafe impl HasParams for Params {}
 
 unsafe impl<T> HasParams for T where T: HasPublic {}
 
 /// A trait indicating that a key has public components.
+#[allow(clippy::missing_safety_doc)]
 pub unsafe trait HasPublic {}
 
 unsafe impl HasPublic for Public {}
 
 unsafe impl<T> HasPublic for T where T: HasPrivate {}
 
 /// A trait indicating that a key has private components.
+#[allow(clippy::missing_safety_doc)]
 pub unsafe trait HasPrivate {}
 
 unsafe impl HasPrivate for Private {}