std: Move the owned module from core to std

The compiler was updated to recognize that implementations for ty_uniq(..) are
allowed if the Box lang item is located in the current crate. This enforces the
idea that libcore cannot allocated, and moves all related trait implementations
from libcore to libstd.

This is a breaking change in that the AnyOwnExt trait has moved from the any
module to the owned module. Any previous users of std::any::AnyOwnExt should now
use std::owned::AnyOwnExt instead. This was done because the trait is intended
for Box traits and only Box traits.

[breaking-change]
Allow blocks in const expressions

Only blocks with tail expressions that are const expressions
and items are allowed.
Add tests for from_bits.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Replaced ~T by Box<T> in manual
Implements Default trait for BigInt and BigUint
Fix #8391

Closes #8391
check_match: get rid of superfluous clones
std, core: Generate unicode.rs using unicode.py
core: Use appropriately sized integers for codepoints and bytes
core: Move Hangul decomposition into unicode.rs
std: Rename str::Normalizations to str::Decompositions

The Normalizations iterator has been renamed to Decompositions.
It does not currently include all forms of Unicode normalization,
but only encompasses decompositions.
If implemented recomposition would likely be a separate iterator
which works on the result of this one.

[breaking-change]
docs: Add a not found page
add a line to the example to clarify semantics

This is to clarify that match construct doesn't define a new variable, since I
observed a person reading the Rust tutorial who seemed to incorrectly think
that it did. Fixes https://github.com/mozilla/rust/issues/13571 .
rustc: Make std_inject valid for pretty-printer

Inject `extern crate {std, native}` before `use` statements.
Add `#![feature(glob)]` since `use std::prelude::*` is used.

(Unfortunately `rustc --pretty expanded` does not converge,
since `extern crate` and `use std::prelude::*` is injected at every
iteration.)
pprust: Add parentheses to some Expr

Some `Expr` needs parentheses when printed. For example, without
parentheses, `ExprUnary(UnNeg, ExprBinary(BiAdd, ..))` becomes
`-lhs + rhs` which is wrong.

Those cases don't appear in ordinary code (since parentheses are
explicitly added) but they can appear in manually crafted ast by
extensions.
pprust: Fix asm output
pprust: Print `&&e` instead of `& &e`
pprust: Remove unnecessary && of `print_tt`
libsyntax: Workaround pprust `for` issue
test: Add missing `#![feature(managed_boxes)]`

The tests use managed boxes, but are not perfectly feature-gated because
they use `@` inside macros. (It causes issue after `--pretty expanded`.)