Iterator documentation fixes

Fixes two typos and one incorrect description.
Alter rust.css to make the documentation look more appealing
Visitor refactoring: Step 1, couple (Env, vt<Env>) together in a tuple.
Fix linebreak and whitespace issues to placate make tidy.
auto merge of #7073 : influenza/rust/iterator-doc-fixes, r=catamorphism

This commit fixes two typos and an incorrect description.
Properly translate calls to default methods in a number of cases. Closes #4350.
Drop some dead method handling code.
Fix a lot of the handling of default methods and type parameters. Closes #4099, #4102.
Merge branch 'moz-incoming' into fsk-visitor-refactoring
Fix a test-predicated use of the visit.rs api.
auto merge of #7084 : pnkfelix/rust/fsk-visitor-refactoring, r=pnkfelix

This step 1 in my plan for issue #7081: Refactor visit.rs with a `@Visitor` trait.
auto merge of #7077 : SiegeLord/rust/new_css, r=pnkfelix

I was making documentation for my own little Rust project, and I was somewhat unhappy with how the documentation looked. While many of the issues are endemic to how rustdoc generates its output, you can get pretty far in making the documentation readable by using a better CSS style.

This commit alters the CSS style used in Rust's documentation in order to make the various sections stand out more. You can see an example of its usage in my own project's documentation: http://siegelord.github.io/RustGnuplot/#implementation-for-figureself-where-self. I showed it to some people on IRC and they suggested that I make a pull request here. I tested it on the only browser that matters, but also Chrome and Opera.
auto merge of #7091 : msullivan/rust/default-methods, r=graydon

r? @nikomatsakis
Rename all files with the 'rc' extension
Deny common lints by default for lib{std,extra}