De-realstd os::args

With the test runner using ::std::os::args(), and std::std::os now being
a re-export of realstd::os, there's no more need for realstd stuff
mucking up rt::args.

Remove the one test of os::args(), as it's not very useful and it won't
work anymore now that rt::args doesn't use realstd.
auto merge of #14423 : Kimundi/rust/static_regex, r=alexcrichton

This patch changes the internals of `Regex` and `regex!()` such that

```rust
static RE: Regex = regex!(...);
```

is valid. It doesn't change anything about the actual regex implementation, it just changes the type to something that can be constructed as a const expression.
Fix to tutorial
auto merge of #14430 : kballard/rust/squelch_os_warning, r=alexcrichton

Clean up the re-exports of various modules in `std::std`, and remove the
`realstd` stuff from `std::rt::args`.
Minor fixes to `std::str` docs

This tweaks the `std::str` docs to compensate for the recent shift from `~str`
to `String`.
Update tutorial, see issue #13578
Allow $foo:block nonterminals in expression position

Fixes #13678.
auto merge of #14432 : kballard/rust/nt_block, r=huonw

Fixes #13678.
mark non-immediate by-value parameters as non-null
auto merge of #14300 : cmr/rust/enum-size-lint, r=kballard

See commits for details.
handle attributes for non-immediate types first

Slices are non-immediate and were not having these attributes applied.
auto merge of #14439 : thestinger/rust/nonnull, r=luqmana
syntax: Add a source field to `Local` for tracking if it comes from `let`s or `for`s.
auto merge of #14374 : swgillespie/rust/swgillespie-tutorial, r=alexcrichton

The current tutorial says that the only way to get master is to build from source, which isn't true anymore - nightly binaries and an installer for Mac OS X are now available at the install page: http://www.rust-lang.org/install.html . Feedback very much welcome! Addresses issue #13578.
Improve docs for core::tuple
auto merge of #14440 : Sawyer47/rust/tuple-doc, r=alexcrichton
syntax: desugar a `for` loop to a let binding to get better error
messages when the pattern is refutable.

This means the compiler points directly to the pattern and said that the
problem is the pattern being refutable (rather than just saying that
some value isn't covered in the `match` as it did previously).

Fixes #14390.
rustc: provide more precise information about refutable patterns.

The compiler now points exactly which part(s) of a pattern are
refutable, rather than just highlighting the whole pattern.
std: Remove String::from_owned_str as it's redundant

[breaking-change]
rustc: Use rust strings for failure arguments

This avoids having to perform conversions from `*u8` to `&'static str` which can
suck in a good deal of code.

Closes #14442