Update AUTHORS.txt
Remove a warning  (./configure: 1140: [: unexpected operator) when built with --disable-manage-submodules
How about a less cringe-worthy double-failure message?
mk: Move rust_test_helpers out of libstd

There's no need to distribute these ABI helpers for tests with the standard rust
distribution they're only needed for our tests.

Closes #2665
Fix documentation for `slice()`

Fixes https://github.com/mozilla/rust/issues/14577
Document BigInt's new and from_slice methods

Fixes https://github.com/mozilla/rust/issues/14639
Change to_str().to_string() to just to_str()
auto merge of #14667 : aochagavia/rust/pr2, r=huonw
auto merge of #14668 : aochagavia/rust/pr3, r=alexcrichton

Closes https://github.com/mozilla/rust/issues/14577
Closes https://github.com/mozilla/rust/issues/14639
auto merge of #14671 : aochagavia/rust/patch-1, r=alexcrichton
auto merge of #14673 : sylvestre/rust/master, r=alexcrichton

 Remove a warning (./configure: 1140: [: unexpected operator) when built with --disable-manage-submodules
auto merge of #14676 : brson/rust/double-rainbow, r=alexcrichton
auto merge of #14677 : alexcrichton/rust/issue-2665, r=brson

There's no need to distribute these ABI helpers for tests with the standard rust
distribution they're only needed for our tests.

Closes #2665
Implement #[plugin_registrar]
Use phase(plugin) in bootstrap crates

Do this to avoid warnings on post-stage0 builds.
Use phase(plugin) in other crates
Use phase(plugin) in tests
Convert libraries to use #[plugin_registrar]
Convert tests to use #[plugin_registrar]
Add a test for deprecated phase(syntax)