Prepared std::sys for removal, and made begin_unwind simpler

- `begin_unwind` is now generic over any `T: Any + Send`.
- Every value you fail with gets boxed as an `~Any`.
- Because of implementation details, `&'static str` and `~str` are still
  handled specially behind the scenes.
- Changed the big macro source string in libsyntax to a raw string
  literal, and enabled doc comments there.

src/test/compile-fail/fail-expr.rs

@@ -1,13 +0,0 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// error-pattern:failed to find an implementation of trait std::sys::FailWithCause for int
-
-fn main() { fail!(5); }

src/test/compile-fail/fail-type-err.rs

@@ -1,12 +0,0 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// error-pattern:failed to find an implementation of trait std::sys::FailWithCause for ~[int]
-fn main() { fail!(~[0i]); }

src/test/run-fail/fail-macro-send_str.rs

@@ -1,15 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// error-pattern:failed at 'test-fail-send-str'
-
-fn main() {
-    fail!("test-fail-send-str".into_send_str());
-}

src/test/run-pass/unit-like-struct-drop-run.rs

@@ -25,6 +25,6 @@ pub fn main() {
         let _b = Foo;
     };
 
-    let s = x.unwrap_err().move::<SendStr>().unwrap();
+    let s = x.unwrap_err().move::<&'static str>().unwrap();
     assert_eq!(s.as_slice(), "This failure should happen.");
 }