Add missing copyright/license statements on all .rs files

(Yes, I have Chelsea's permission.)

src/rust/external/external.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 use libc::{c_char, c_int};
 use std::ffi::CString;
 

src/rust/protover/ffi.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 //! FFI functions, only to be called from C.
 //!
 //! Equivalent C versions of this api are in `src/or/protover.c`

src/rust/protover/protover.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 use external::c_tor_version_as_new_as;
 
 use std::str::FromStr;

src/rust/protover/tests/protover.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 extern crate protover;
 
 #[test]

src/rust/smartlist/lib.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 extern crate libc;
 
 mod smartlist;

src/rust/smartlist/smartlist.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 use std::slice;
 use libc::{c_char, c_int};
 use std::ffi::CStr;

src/rust/tor_allocate/lib.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 //! Allocation helper functions that allow data to be allocated in Rust
 //! using tor's specified allocator. In doing so, this can be later freed
 //! from C.

src/rust/tor_allocate/tor_allocate.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 use libc::{c_char, c_void};
 use std::{ptr, slice, mem};
 

src/rust/tor_util/ffi.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 //! FFI functions to announce Rust support during tor startup, only to be
 //! called from C.
 //!

src/rust/tor_util/lib.rs

+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
 //! Small module to announce Rust support during startup for demonstration
 //! purposes.
 //!