an attempt at a singleton pausible idle callback for each scheduler. suffers from nondeterministic deadlock and also pending scheduler messages on scheduler shutdown.
std::rt: Touch up idle logic
std::rt: Fix a race in UvRemoteCallback's dtor that misses callbacks

Full description in comments.
Moved the logic for a pausible idle callback into a new type - PausibleIdleCallback and placed the appropriate signatures in rtio and implementation into uvio.
A round of code cleaning for the primary scheduler code. Comments have been updated, a minor amount of support type restructing has happened, methods have been reordered, and some duplicate code has been purged.
Rangechange the log message truncation limit.
Make supertrait methods callable on object types.

This requires changes to method search and to codegen. We now emit a
vtable for objects that includes methods from all supertraits.
Closes #4100.

Also, actually populate the cache for vtables, and also key it by type
so that it actually works.
clean whitespace :/
rustpkg: Un-ignore most of the remaining tests

This necessitated some cleanup to how we parse library filenames
when searching for libraries, since rustpkg may now create filenames
that contain '-' characters. Also cleaned up how rustpkg passes the
sysroot to a custom build script.
doc: add condition tutorial
std: Restore dynamic borrow tracking
auto merge of #8548 : catamorphism/rust/unignore-rustpkg-tests, r=catamorphism

r? @brson This necessitated some cleanup to how we parse library filenames
when searching for libraries, since rustpkg may now create filenames
that contain '-' characters. Also cleaned up how rustpkg passes the
sysroot to a custom build script.
Upgrade llvm to current HEAD

* This has one workaround patch (everything's testing just fine...)
* I reworked the fixedstacksegment attribute to be specified with a string
  rather than using a keyword and an integer and modifying the parser
* I added a "no-split-stack" attribute along the same lines as the
  "fixedstacksegment" attribute for #1226
Port lint.rs from oldvisit to <V:Visit> trait API.  Less mechanical port.

That is, there was lots more hacking than the other more-mechanical
ports Felix did.

There's also a strange pattern that I hacked in to accommodate the
Outer/Inner traversal structure of the existing code (which was
previously encoding this by untying the Y-combinator style knot of the
vtable, and then retying it but superimposing new methods that "stop
at items").  I hope either I or someone else can come back in the
future and replace this ugliness with something more natural.

Added boilerplate macro; all the OuterLint definitions are the same
(but must be abstracted over implementing struct, thus the macro).

Revised lint.rs use declarations to make ast references explicit.
Also removed unused imports.
remove trailing whitespace to placate make tidy.
add line break post dbaupp review.
auto merge of #8638 : pnkfelix/rust/fsk-visitor-vpar-defaults-step5, r=huonw

"non-mechanical" : there was lots more hacking than the other more-mechanical ports Felix did.

r? @huonw.  (Or @nikomatsakis ; I just want someone to sanity-check this.  Its not a thing of beauty.)

Followup to #8623.  (See #8527, which was step 1 of 5, for the full outline.  Part of #7081.)

Notes on the change follow.

There's also a strange pattern that I hacked in to accommodate the
Outer/Inner traversal structure of the existing code (which was
previously encoding this by untying the Y-combinator style knot of the
vtable, and then retying it but superimposing new methods that "stop
at items").  I hope either I or someone else can come back in the
future and replace this ugliness with something more natural.

Added boilerplate macro; all the OuterLint definitions are the same
(but must be abstracted over implementing struct, thus the macro).

Revised lint.rs use declarations to make ast references explicit.
Also removed unused imports.
auto merge of #8463 : brson/rust/borrowck, r=nmatsakis,nikomatsakis

r? @nikomatsakis
Fix LLVM compilation issues and use the new attrs

This implements #[no_split_stack] and also changes #[fast_ffi] to using the new
"fixedstacksegment" string attribute instead of integer attribute.
auto merge of #8566 : toddaaro/rust/idle-opt+cleaning, r=catamorphism,brson

Instead of a furious storm of idle callbacks we just have one. This is a major performance gain - around 40% on my machine for the ping pong bench.

Also in this PR is a cleanup commit for the scheduler code. Was previously up as a separate PR, but bors load + imminent merge hell led me to roll them together. Was #8549.