make deleted function public for AsyncUDPSocket.h (#1603)

Summary:
Ref: https://abseil.io/tips/143

Pull Request resolved: https://github.com/facebook/folly/pull/1603

Differential Revision: D29034248

Pulled By: yfeldblum

fbshipit-source-id: 87ae1970eab3f067d71a480fc7a95b18e2041c6d

folly/io/async/AsyncUDPSocket.h

@@ -39,6 +39,9 @@ class AsyncUDPSocket : public EventHandler {
  public:
   enum class FDOwnership { OWNS, SHARED };
 
+  AsyncUDPSocket(const AsyncUDPSocket&) = delete;
+  AsyncUDPSocket& operator=(const AsyncUDPSocket&) = delete;
+
   class ReadCallback {
    public:
     struct OnDataAvailableParams {
@@ -493,9 +496,6 @@ class AsyncUDPSocket : public EventHandler {
   ReadCallback* readCallback_;
 
  private:
-  AsyncUDPSocket(const AsyncUDPSocket&) = delete;
-  AsyncUDPSocket& operator=(const AsyncUDPSocket&) = delete;
-
   void init(sa_family_t family, BindOptions bindOptions);
 
   // EventHandler