Little typo fix

- ./hello_world which is not recognized on Windows fixed.
- .exe extension added.
- Little rewriting.
add example for from_byte() documenation
Add `impl Show for &Show`

This makes printing a `Show` trait object much easier.
core: Reorganize slice module.

This is just moving things around so they are defined in a logical order.
core: Remove the unnecessary 'traits' module from 'slice'

This is only breaking for code that references the empty `slice::traits`
module.

[breaking-change]
auto merge of #15247 : smenardpw/rust/patch-1, r=alexcrichton

./hello_world is not recognized on Windows.
We can type either hello_world or hello_world.exe to run the executable. I chose "hello_world.exe", which seems more conventional on Windows.
auto merge of #15271 : jasonthompson/rust/docs/str, r=huonw

I'm working on adding examples to the API documentation. Should future pull requests include examples for more than one function? Or is this about the right size for a pull request?
librustc: Permit by-value-self methods to be invoked on objects
referenced by boxes.

This is done by creating a shim function that handles the cleanup of the
box properly.

Closes #10672.
auto merge of #15242 : pcwalton/rust/self-in-trait-methods, r=alexcrichton

I can't believe this worked! I believe that the way the ABI and
immediates work mean that this Just Works.

Closes #10672.

r? @alexcrichton
auto merge of #15281 : alexcrichton/rust/show-for-show, r=kballard

This makes printing a `Show` trait object much easier.
Vim syntax file types and traits cleanup
rustdoc: incorporate stability index throughout

This commit hooks rustdoc into the stability index infrastructure in two
ways:

1. It looks up stability levels via the index, rather than by manual
attributes.

2. It adds stability level information throughout rustdoc output, rather
than just at the top header. In particular, a stability color (with
mouseover text) appears next to essentially every item that appears
in rustdoc's HTML output.

Along the way, the stability index code has been lightly refactored.
libstd: set baseline stability levels.

Earlier commits have established a baseline of `experimental` stability
for all crates under the facade (so their contents are considered
experimental within libstd). Since `experimental` is `allow` by
default, we should use the same baseline stability for libstd itself.

This commit adds `experimental` tags to all of the modules defined in
`std`, and `unstable` to `std` itself.
auto merge of #15263 : aturon/rust/rustdoc-stability-index, r=alexcrichton

This commit hooks rustdoc into the stability index infrastructure in two
ways:

1. It looks up stability levels via the index, rather than by manual
attributes.

2. It adds stability level information throughout rustdoc output, rather
than just at the top header. In particular, a stability color (with
mouseover text) appears next to essentially every item that appears
in rustdoc's HTML output.

Along the way, the stability index code has been lightly refactored.
auto merge of #15288 : brson/rust/cleanslice, r=alexcrichton

This does two things:

* Reorganizes the declaration order to be more readable, less random.
* Removes the `slice::traits` module, a public module that does nothing but declare impls of `cmp` traits.
auto merge of #15289 : aturon/rust/libstd-stability, r=alexcrichton

Earlier commits have established a baseline of `experimental` stability
for all crates under the facade (so their contents are considered
experimental within libstd). Since `experimental` is `allow` by
default, we should use the same baseline stability for libstd itself.

This commit adds `experimental` tags to all of the modules defined in
`std`, and `unstable` to `std` itself.
Add examples for from_utf8_owned, from_char, from_chars, from_byte
auto merge of #15301 : jasonthompson/rust/docs/str2, r=alexcrichton
Improve rustdocs for Rc, add examples
doc: Clarify that an error is a compiler error

This was asked on HN, and it's easy to clarify.