Free functions deprecated. UnicodeChar experimental pending
final decisions about prelude.

Extension traits for primitive types should be by-value.

[breaking-change]

[breaking-change]

Methods on primitmive Copy types generally should take `self`.

[breaking-change]

The `Char` trait itself may go away in favor of primitive inherent
methods. Still some questions about whether the preconditions are
following the final error handling conventions.

Prefer the methods.

For now we are preferring free functions for primitive ctors,
so they are marked 'unstable' pending final decision. The
methods on `Char` are 'deprecated'.

Missing method to pair with len_utf8.

"bytes" is redundant.

Deprecate the old.

This fits the naming of `to_digit` and `from_digit`. Leave
the old name deprecated.

'Numeric' is the proper name of the unicode character class,
and this frees up the word 'digit' for ascii use in libcore.

Since I'm going to rename `Char::is_digit_radix` to
`is_digit`, I am not leaving a deprecated method in place,
because that would just cause name clashes, as both
`Char` and `UnicodeChar` are in the prelude.

[breaking-change]

This is the only free function not part of the trait.

Vim plugins shouldn't override user settings unless they ask!

Stops the plugin from modifying the users settings by default
instead makes them opt-in with `g:rust_recommended_style`

This allows encoding to UTF-16 something that is not in UTF-8, e.g. a `[char]` UTF-32 string.

This might help with servo/servo#4023

Fix #17574

Fixies #11671

This commit changes default relative libdir 'lib' to a relative libdir calculated using LIBDIR provided by --libdir configuration option. In case if no option was provided behavior does not change.

This PR completes the removal of the runtime system and green-threaded abstractions as part of implementing [RFC 230](https://github.com/rust-lang/rfcs/pull/230).

Specifically:

* It removes the `Runtime` trait, welding the scheduling infrastructure directly to native threads.

* It removes `libgreen` and `libnative` entirely.

* It rewrites `sync::mutex` as a trivial layer on top of native mutexes. Eventually, the two modules will be merged.

* It hides the vast majority of `std::rt`.

This completes the basic task of removing the runtime system (I/O and scheduling) and components that depend on it. 

After this lands, a follow-up PR will pull the `rustrt` crate back into `std`, turn `std::task` into `std::thread` (with API changes to go along with it), and completely cut out the remaining startup/teardown sequence. Other changes, including new [TLS](https://github.com/rust-lang/rfcs/pull/461) and synchronization are in the RFC or pre-RFC phase.

Closes #17325
Closes #18687

[breaking-change]

r? @alexcrichton 

Previously, the entire runtime API surface was publicly exposed, but
that is neither necessary nor desirable. This commit hides most of the
module, using librustrt directly as needed. The arrangement will need to
be revisited when rustrt is pulled into std.

[breaking-change]

Previously, sync::mutex had to split between green and native runtime
systems and thus could not simply use the native mutex facility.

This commit rewrites sync::mutex to link directly to native mutexes; in
the future, the two will probably be coalesced into a single
module (once librustrt is pulled into libstd wholesale).

With runtime removal complete, there is no longer any reason to provide
libgreen.

[breaking-change]

With runtime removal complete, there's nothing left of libnative. This
commit removes it.

Fixes #18687

[breaking-change]

This commit removes most of the remaining runtime infrastructure related
to the green/native split. In particular, it removes the `Runtime` trait
and instead inlines the native implementation.

Closes #17325

[breaking-change]

Closes #18415

This links [`std::str`](http://doc.rust-lang.org/std/str/index.html) documentation to [literals](http://doc.rust-lang.org/reference.html#literals) in the reference guide and collects examples of literals into one group at the beginning of the section. ~~The new tables are not exhaustive (some escapes were skipped) and so I try to link back to the respective sections where more detail is located.~~ The tables are are mostly exhaustive. I misunderstood some of the whitespace codes.

I don't think the tables actually look that nice if that's important and I'm not sure how it could be improved. I think it does do a good job of collecting available options together. I think listing the escapes together is particularly helpful because they vary with type and are embedded in paragraphs.

[EDIT]
The [ascii table](http://man-ascii.com/) is here and may be useful.

I have also renamed `fail` to `panic` in some non-documentation comments, where I thought it mattered.
Fixes #18677 

cc @steveklabnik 

In the general case, at least, it is not possible to make an object out of an unsized type. This is because the object type would have to store the fat pointer information for the `self` value *and* the vtable -- meaning it'd have to be a fat pointer with three words -- but for the compiler to know that the object requires three words, it would have to know the self-type of the object (is `self` a thin or fat pointer?), which of course it doesn't.

Fixes #18333.

r? @nick29581 

This macro is very rarely used, so there is no need (and it is better)
for it to avoid the abbreviation.

Closes rust-lang/rfcs#467.

This allows encoding to UTF-16 something that is not in UTF-8, e.g. a
`[char]` UTF-32 string.

This might help with https://github.com/servo/servo/issues/4023