Mark &mut parameters as noalias
auto merge of #6742 : Aatch/rust/mut-noalias, r=thestinger

This marks `&mut` function arguments with the `noalias` attribute. Since the borrow checker enforces this property, this is worth doing.

I'm not sure if the place I'm doing it in is ideal, but it generates the correct code.

Closes #6350
Add documentation for libstd/bool.rs.

There was some before, but now we have a big header, as well as
lots of individual bits of documentation.
auto merge of #6700 : ben0x539/rust/nestvariantdocs, r=thestinger

This indents all but the first line of multi-line annotations for individual enum variants with four spaces so that pandoc will recognize everything as belonging to the same list item.

Since that introduces `<p>` tags for some list items, I've gone ahead and inserted blank lines after each list item so that consistently get `<p>` tags for all `<li>`s documenting variants. It's a bit less compact now but still tolerable, I think.
auto merge of #6748 : steveklabnik/rust/bool_docs, r=thestinger

There was some before, but now we have a big header, as well as
lots of individual bits of documentation.
rustdoc: insert blank lines between consecutive doc comment blocks

This is to prevent, for example,

    /**
     * foo
     */

    /// bar

    mod m {
      //! baz
    }

from being rendered into a single paragraph "foo bar baz" by markdown.