closes rust-lang#39974

r? @Mark-Simulacrum

This should include a fix for rust-lang/cargo#4091 with an updated version of
libgit2.

Closes rust-lang/cargo#4091

Mark various items and fields as private or pub(crate), and remove a function that turns out to be unused.
These are not used anywhere in-tree, but I guess it's a [breaking-change] for plugins.

The previous commit removed them from the public API, this rewrites the use statements to get rid of the non-standard re-exports.

…eddyb

Remove all instances of fragment_infos and fragment sets

Remove unused fragment structs. This was suggested by @eddyb in IRC: [botbot link](https://botbot.me/mozilla/rustc/2017-05-23/?msg=86016574&page=2).

…ulacrum

regression test for rust-lang#39974

closes rust-lang#39974

r? @Mark-Simulacrum

…tsakis

Updated locked version of libgit2

This should include a fix for rust-lang/cargo#4091 with an updated version of
libgit2.

Closes rust-lang/cargo#4091

Allow variadic functions with cdecl calling convention.

Fixes rust-lang#40244.

…ed-tail, r=eddyb

extend `struct_tail` to operate over tuples

Not 100% sure why this got exposed when it wasn't before, but this struct definitely seems wrong.

Fixes rust-lang#42110

r? @eddyb

…ent, r=alexcrichton

Docs: impls of PartialEq/PartialOrd/Ord must agree

Fixes rust-lang#41270.

This PR brings two improvements to the docs:

1. Docs for `PartialEq`, `PartialOrd`, and `Ord` clarify that their implementations must agree.
2. Fixes a subtle bug in the Dijkstra example for `BinaryHeap`, where the impls are inconsistent.
Thanks @Rufflewind for spotting the bug!

r? @alexcrichton
cc @frankmcsherry

Remove unused APIs from rustc_trans

There were public re-exports of some rustc modules dating back to 2011 or so. While I was at it, some functions and modules were public but never used outside the crate. I made them private or `pub(crate)` as appropriate and in one case removed an unused function.