moveonly: move IsSelectableSocket() from compat.h to sock.{h,cpp}

To be converted to a method of the `Sock` class.

src/compat/compat.h

@@ -109,14 +109,6 @@ typedef char* sockopt_arg_type;
 #define USE_POLL
 #endif
 
-bool static inline IsSelectableSocket(const SOCKET& s) {
-#if defined(USE_POLL) || defined(WIN32)
-    return true;
-#else
-    return (s < FD_SETSIZE);
-#endif
-}
-
 // MSG_NOSIGNAL is not available on some platforms, if it doesn't exist define it as 0
 #if !defined(MSG_NOSIGNAL)
 #define MSG_NOSIGNAL 0

src/util/sock.cpp

@@ -117,6 +117,14 @@ int Sock::GetSockName(sockaddr* name, socklen_t* name_len) const
     return getsockname(m_socket, name, name_len);
 }
 
+bool IsSelectableSocket(const SOCKET& s) {
+#if defined(USE_POLL) || defined(WIN32)
+    return true;
+#else
+    return (s < FD_SETSIZE);
+#endif
+}
+
 bool Sock::Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred) const
 {
     // We need a `shared_ptr` owning `this` for `WaitMany()`, but don't want

src/util/sock.h

@@ -267,6 +267,8 @@ private:
     void Close();
 };
 
+bool IsSelectableSocket(const SOCKET& s);
+
 /** Return readable error string for a network error code */
 std::string NetworkErrorString(int err);