Add some doc examples to lib{green,native}

"How do I start in libX" is a common question that I've seen, so I figured
putting the examples in as many places as possible is probably a good idea.
Make semver::Version fields public
moved collections from libextra into libcollections
Implement std::fmt::Show for semver::{Identifier, Version}
Add new function str::from_utf8_lossy()

from_utf8_lossy() takes a byte vector and produces a ~str, converting
any invalid UTF-8 sequence into the U+FFFD REPLACEMENT CHARACTER.

The replacement follows the guidelines in §5.22 Best Practice for U+FFFD
Substitution from the Unicode Standard (Version 6.2)[1], which also
matches the WHATWG rules for utf-8 decoding[2].

[1]: http://www.unicode.org/versions/Unicode6.2.0/ch05.pdf
[2]: http://encoding.spec.whatwg.org/#utf-8
Hoist path::Display on top of from_utf8_lossy()
auto merge of #12010 : HeroesGrave/rust/libcollection, r=alexcrichton

Part of #8784

Changes:
- Everything labeled under collections in libextra has been moved into a new crate 'libcollection'.
- Renamed container.rs to deque.rs, since it was no longer 'container traits for extra', just a deque trait.
- Crates that depend on the collections have been updated and dependencies sorted.
- I think I changed all the imports in the tests to make sure it works. I'm not entirely sure, as near the end of the tests there was yet another `use` that I forgot to change, and when I went to try again, it started rebuilding everything, which I don't currently have time for. 

There will probably be incompatibility between this and the other pull requests that are splitting up libextra. I'm happy to rebase once those have been merged.

The tests I didn't get to run should pass. But I can redo them another time if they don't.
auto merge of #12062 : kballard/rust/from_utf8_lossy, r=huonw

`from_utf8_lossy()` takes a byte vector and produces a `~str`, converting
any invalid UTF-8 sequence into the U+FFFD REPLACEMENT CHARACTER.

The replacement follows the guidelines in §5.22 Best Practice for U+FFFD
Substitution from the Unicode Standard (Version 6.2)[1], which also
matches the WHATWG rules for utf-8 decoding[2].

[1]: http://www.unicode.org/versions/Unicode6.2.0/ch05.pdf
[2]: http://encoding.spec.whatwg.org/#utf-8

Closes #9516.
auto merge of #12083 : bjz/rust/semver, r=huonw
Span debugger
Correct span for ExprFnBlock, ExprMethodCall, ExprParen
Add comments to span debugger
auto merge of #12087 : sanxiyn/rust/show-span, r=huonw
Add unimplemented! macro
Add missing test for unreachable! macro
Removed prelude::* from libstd files.

This replaces the imports from the prelude with the re-exported symbols.
Cleaned up imports per coding standards.

No functional changes; just style.
auto merge of #12075 : chromatic/rust/gh_11983_deglob_std, r=alexcrichton

This replaces the imports from the prelude with the re-exported symbols.
Clean up formatting in macros module
Added tests to make tidy