rustc: rename ty::vstore and its variants to UpperCamelCase.
rustc: use VstoreFixed's length in crate-independent type hashes.
rustc: move mutability from ty_vec and ty_trait to VstoreSlice and RegionTraitStore.
Document the nullable pointer optimization in the FFI guide

Closes #8748
Register snapshots.

This is the first snap based on mingw-w64.
std: Be sure to call pthread_attr_destroy

On some OSes (such as freebsd), pthread_attr_init allocates memory, so this is
necessary to deallocate that memory.

Closes #13420
auto merge of #13451 : cmr/rust/doc-ffi, r=brson

Closes #8748
rustc: fix the fallout from moving mutability into VstoreSlice and RegionTraitStore.
auto merge of #13453 : brson/rust/snappies, r=alexcrichton

This is the first snap based on mingw-w64.
auto merge of #13457 : alexcrichton/rust/issue-13420, r=thestinger

On some OSes (such as freebsd), pthread_attr_init allocates memory, so this is
necessary to deallocate that memory.

Closes #13420
libtest: rename `BenchHarness` to `Bencher`
Closes #12640
auto merge of #13424 : eddyb/rust/ty-mut-in-store, r=nikomatsakis

Cleans up some remnants of the old mutability system and only allows vector/trait mutability in `VstoreSlice` (`&mut [T]`) and `RegionTraitStore` (`&mut Trait`).
Add more type signatures to the docs; tweak a few of them.

Someone reading the docs won't know what the types of various things
are, so this adds them in a few meaningful places to help with
comprehension.

cc #13423.
auto merge of #13236 : liigo/rust/rename-benchharness, r=huonw

Closes #12640

based on PR #13030, rebased, and passed all tests.
auto merge of #13458 : huonw/rust/doc-signatures, r=alexcrichton

Add more type signatures to the docs; tweak a few of them.

Someone reading the docs won't know what the types of various things
are, so this adds them in a few meaningful places to help with
comprehension.

cc #13423.
Parameterize contains_nul for BytesContainer.
Simplify GenericPath::set_extension.
auto merge of #13395 : Ryman/rust/bytecontainer_impl_container, r=alexcrichton

Also some minor cleanup in Path related to this.
Use more precise span when reporting semicolon hint

When reporting "consider removing this semicolon" hint message, the
offending semicolon may come from macro call site instead of macro
itself. Using the more appropriate span makes the hint more helpful.

Closes #13428.