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

Also touch up use of 'pub' and move some tests around so the tested functions
don't have to be 'pub'

These couldn't be overridden and so ended up being quite restrictive. This has
the side effect of changing the stringification of ~vecs, but nothing in
relied on this. Closes #4869.

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

Needs a snapshot to remove stage0 extfmt export in core

Changed a test to use intrinsics.rs and changed a few lines that were too long, had bad whitespace, etc.

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