Closes #12386. Removed 'pub mod' doc-comments in std::io's mod.rs file. Added summary doc-comments to test.rs, util.rs and stdio.rs.
tutorial: clearer explanation of freezing.

- "Lending an immutable pointer" might be confusing. It was not discussed why borrowed pointers are immutable in the first place.
- Make it clear that the borrowed pointers are immutable even if the variable was declared with `mut`.
- Make it clear that we cannot even assign anything to the variable while its value is being borrowed.

tutorial: change "--" to an em-dash.

tutorial: change instances of "--" to em-dash.
auto merge of #12547 : jagtalon/rust/jag/rust/tutorial-freezing, r=pnkfelix

- "Lending an immutable pointer" might be confusing. It was not discussed why borrowed pointers are immutable in the first place.
- Make it clear that the borrowed pointers are immutable even if the variable was declared with `mut`.
- Make it clear that we cannot even assign anything to the variable while its value is being borrowed.

tutorial: change "--" to an em-dash.

tutorial: change instances of "--" to em-dash.
tutorial: Missing tildes around .notrust block

Adds a missing tilde to the end and the start of two .notrust blocks.
Rename a few typeck method-related structures to UpperCamelCase.
Replace callee_id with information stored in method_map.
auto merge of #12571 : eddyb/rust/kill-callee-id, r=nikomatsakis

Every method call and overloaded operator had a `callee_id` that was be used to store the method type and type substitutions, that information is now stored in the `method_map`, alongside the method's origin.
auto merge of #12570 : kyrias/rust/master, r=cmr

Adds a missing tilde to the end and the start of two .notrust blocks.
rustc: Explicitly mention type params with missing `'static` bounds

Also renames `check_durable` to `check_static` and removes the outdated
comment.
auto merge of #12490 : zslayton/rust/doc-fix-12386, r=alexcrichton

Attn: @huonw 

Addresses #12386.
auto merge of #12572 : lifthrasiir/rust/owned-ptr-static-bound, r=alexcrichton

This is inspired by the [question](http://www.reddit.com/r/rust/comments/1yy57k/unsolved_question_from_irc/) (re-)posted to /r/rust. The error message in this question correctly states that one should add `'static` to the trait bounds, but does not state which trait bounds. This PR makes that explicit by appending two words.

This also renames `check_durable` to `check_static` and removes the outdated comment as a cleanup.
Rename all variables that have uppercase characters in their names to use only lowercase characters
Add lint for variable names that contain uppercase characters
Rename struct fields with uppercase characters in their names to use lowercase
Emit the uppercase variable lint for struct fields that have names with uppercase characters