Properly static lib packaging

Fixes #18574
Prepend should be append in the 30 minute intro

The examples are about adding to the end of the array, not the
beginning.
Make TyTrait embed a `TraitRef`, so that when we extend TraitRef, it naturally carries over to object types.

I wanted to embed an `Rc<TraitRef>`, but I was foiled by the current
static rules, which prohibit non-Sync values from being stored in
static locations. This means that the constants for `ty_int` and so
forth cannot be initialized.
Update parser with `for` syntax
Update tests where we don't report errors twice anymore
Purge the old `once_fns`, which are not coming back
Fix tidy error
Add BitXor to EnumSet.
syntax: Use UFCS in the expansion of `#[deriving(PartialOrd)]`
Add tests for BitAnd and BitXor.
Update Partial/Total Eq/Ord terminology
Reword &str coercion into viewing
Fix handling of for loop patterns in regionck

When establishing region links within a pattern, use the mem-cat
of the type the pattern matches against (that is, the result
of `iter.next()`) rather than that of the iterator type.

Closes #17068
Closes #18767
Add regression for #17068
Add regression for #18767
mk: Fix Windows cross-build prefix
auto merge of #18743 : nikomatsakis/rust/hrtb-refactor-2, r=pcwalton

Various miscellaneous changes pushing towards HRTB support:

1. Update parser and adjust ast to support `for<'a,'b>` syntax, both in closures and trait bounds. Warn on the old syntax (not error, for stage0).
2. Refactor TyTrait representation to include a TraitRef.
3. Purge `once_fns` feature gate and `once` keyword.

r? @pcwalton 

This is a [breaking-change]:

- The `once_fns` feature is now officially deprecated. Rewrite using normal closures or unboxed closures.
- The new `for`-based syntax now issues warnings (but not yet errors):
  - `fn<'a>(T) -> U` becomes `for<'a> fn(T) -> U`
  - `<'a> |T| -> U` becomes `for<'a> |T| -> U`
Runtime removal: add private sys, sys_common modules

These modules will house the code that used to be part of the runtime system
in libnative. The `sys_common` module contains a few low-level but
cross-platform details. The `sys` module is set up using `#[cfg()]` to
include either a unix or windows implementation of a common API
surface. This API surface is *not* exported directly in `libstd`, but is
instead used to bulid `std::os` and `std::io`.

Ultimately, the low-level details in `sys` will be exposed in a
controlled way through a separate platform-specific surface, but that
setup is not part of this patch.
Remove signal handling.

Since signal handling was only implemented through librustuv, which is
now gone, there's no reason to even provide the API.

[breaking-change]
Runtime removal: refactor fs

This moves the filesystem implementation from libnative into the new
`sys` modules, refactoring along the way and hooking into `std::io::fs`.

Because this eliminates APIs in `libnative` and `librustrt`, it is a:

[breaking-change]

This functionality is likely to be available publicly, in some form,
from `std` in the future.