feat(x509): Implement `Clone` for `X509Store` (#339)

* boring(x509): impl Clone of X509Store

boring/src/x509/store.rs

@@ -125,6 +125,23 @@ foreign_type_and_impl_send_sync! {
     pub struct X509Store;
 }
 
+impl Clone for X509Store {
+    fn clone(&self) -> Self {
+        (**self).to_owned()
+    }
+}
+
+impl ToOwned for X509StoreRef {
+    type Owned = X509Store;
+
+    fn to_owned(&self) -> Self::Owned {
+        unsafe {
+            ffi::X509_STORE_up_ref(self.as_ptr());
+            X509Store::from_ptr(self.as_ptr())
+        }
+    }
+}
+
 impl X509StoreRef {
     /// **Warning: this method is unsound**
     ///