system/fd_util: remove unused function accept_cloexec_nonblock()

src/system/fd_util.h

@@ -64,14 +64,6 @@ fd_set_cloexec(int fd, bool enable);
 int
 pipe_cloexec_nonblock(int fd[2]);
 
-/**
- * Wrapper for accept(), which sets the CLOEXEC and the NONBLOCK flags
- * (atomically if supported by the OS).
- */
-int
-accept_cloexec_nonblock(int fd, struct sockaddr *address,
-			size_t *address_length_r);
-
 /**
  * Portable wrapper for close(); use closesocket() on WIN32/WinSock.
  */