i3-dump-log -f: switch from pthreads to UNIX sockets

fixes #4117

include/ipc.h

@@ -80,13 +80,6 @@ void ipc_new_client(EV_P_ struct ev_io *w, int revents);
  */
 ipc_client *ipc_new_client_on_fd(EV_P_ int fd);
 
-/**
- * Creates the UNIX domain socket at the given path, sets it to non-blocking
- * mode, bind()s and listen()s on it.
- *
- */
-int ipc_create_socket(const char *filename);
-
 /**
  * Sends the specified event to all IPC clients which are currently connected
  * and subscribed to this kind of event.