* Disallow structural records everywhere
* Remove all #[cfg(stage0)] stuff
* Remove the last deprecated modes in libcore
* Un-xfail a test

librustc: Separate the rest of the trait bounds with `+` and stop parsing space-separated ones. rs=plussing

rustc intrinsic. Several files in libcore have been changed to use
these intrinsics.
As of yet, none of the intrinsics are documented.

That will, sadly, require one more snapshot.

correct handling of moves for struct-record update.

Part of #3678.  Fixes #2828, #3904, #4719.

fail

Fix merge conflicts - Issue 4524

"Dual impls" are impls that are both type implementations and trait
implementations. They can lead to ambiguity and so this patch removes them
from the language.

This also enforces coherence rules. Without this patch, records can implement
traits not defined in the current crate. This patch fixes this, and updates
all of rustc to adhere to the new enforcement. Most of this patch is fixing
rustc to obey the coherence rules, which involves converting a bunch of records
to structs.

Because of macros, #[allow(structural_records]] in
extfmt, gc, os, pipes, and run. Will need a snapshot.

After a snapshot, we can take out the set_buffer_ version (pipes
syntax exts use it).

As per #4421

Revert "librustc: Make unqualified identifier searches terminate at the nearest module scope. r=tjc"

This reverts commit a8d37af2.