delete folly::AsyncSocket::OptionMap/OptionKey/emptyOptionMap aliases

Summary: delete the folly::AsyncSocket::OptionMap/OptionKey/emptyOptionMap aliases

Reviewed By: yangchi

Differential Revision: D19963346

fbshipit-source-id: 6beae0961a82d12efd4d784ec390031d9445cd2b

folly/io/async/AsyncSocket.cpp

@@ -62,9 +62,6 @@ static constexpr bool msgErrQueueSupported =
     false;
 #endif // FOLLY_HAVE_MSG_ERRQUEUE
 
-// static members initializers
-const AsyncSocket::OptionMap AsyncSocket::emptyOptionMap;
-
 const AsyncSocketException socketClosedLocallyEx(
     AsyncSocketException::END_OF_FILE,
     "socket closed locally");

folly/io/async/AsyncSocket.h

@@ -380,10 +380,6 @@ class AsyncSocket : virtual public AsyncTransportWrapper {
    */
   virtual NetworkSocket detachNetworkSocket();
 
-  using OptionKey = SocketOptionKey;
-  using OptionMap = SocketOptionMap;
-  static const OptionMap emptyOptionMap;
-
   static const folly::SocketAddress& anyAddress();
 
   /**