std: Remove public bool,tuple,unit modules

This commit modifies rustdoc to not require these empty modules to be public in
the standard library. The modules still remain as a location to attach
documentation to, but the modules themselves are now private (don't have to
commit to an API). The documentation for the standard library now shows all of
the primitive types on the main index page.

src/libstd/tuple.rs

@@ -0,0 +1,66 @@
+// 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.
+
+//! Operations on tuples
+//!
+//! To access a single element of a tuple one can use the following
+//! methods:
+//!
+//! * `valN` - returns a value of _N_-th element
+//! * `refN` - returns a reference to _N_-th element
+//! * `mutN` - returns a mutable reference to _N_-th element
+//!
+//! Indexing starts from zero, so `val0` returns first value, `val1`
+//! returns second value, and so on. In general, a tuple with _S_
+//! elements provides aforementioned methods suffixed with numbers
+//! from `0` to `S-1`. Traits which contain these methods are
+//! implemented for tuples with up to 12 elements.
+//!
+//! If every type inside a tuple implements one of the following
+//! traits, then a tuple itself also implements it.
+//!
+//! * `Clone`
+//! * `PartialEq`
+//! * `Eq`
+//! * `PartialOrd`
+//! * `Ord`
+//! * `Default`
+//!
+//! # Examples
+//!
+//! Using methods:
+//!
+//! ```
+//! #[allow(deprecated)]
+//! # fn main() {
+//! let pair = ("pi", 3.14f64);
+//! assert_eq!(pair.val0(), "pi");
+//! assert_eq!(pair.val1(), 3.14f64);
+//! # }
+//! ```
+//!
+//! Using traits implemented for tuples:
+//!
+//! ```
+//! use std::default::Default;
+//!
+//! let a = (1i, 2i);
+//! let b = (3i, 4i);
+//! assert!(a != b);
+//!
+//! let c = b.clone();
+//! assert!(b == c);
+//!
+//! let d : (u32, f32) = Default::default();
+//! assert_eq!(d, (0u32, 0.0f32));
+//! ```
+
+#![doc(primitive = "tuple")]
+#![stable]