bitv: make benchmarks always return a value

This makes sure that the benchmarked code does not get optimized away.
Also fixed a typo.

Fixes #12118.
arena: fix a typo
bitv: make sure benchmarks run long enough

Previously they were too short (less than 10 ns), so the benchmarker
could not resolve them meaningfully. Now they should run in the order of
100 ns.
Fix LLVM version in configure

Upstream LLVM from VCS already has version 3.6,
configure fixed appropriately to allow building with it
syntax: Fix complexity of string parsing. Closes #16624.
syntax: Test parsing of long binary strings
Use only 400000 characters to test slow string parsing.
make priorityqueue's from_iter use heapify
win64: Add missing #[repr(C)]

Signed-off-by: Peter Atashian <retep998@gmail.com>
auto merge of #16651 : vks/rust/fix-bitv-bench, r=alexcrichton

Fixes #12118.

(I sneaked in an unrelated one-character whitespace fix I spotted while reviewing some benchmarks, if that is not okay, I can create a separate pull request for that.)
librustc: Properly tag upvars in proc's to stop misleading unused_mut warnings.
auto merge of #16659 : brson/rust/slowparse, r=alexcrichton

Note that this contains a 9.5MB test file, but it should compress thoroughly.
auto merge of #16658 : jauhien/rust/fix-llvm, r=thestinger

Upstream LLVM from VCS already has version 3.6,
configure fixed appropriately to allow building with it
auto merge of #16663 : Gankro/rust/heapify, r=alexcrichton

Heapify is O(n), extend as currently implemented is O(nlogn). No brainer.

Currently investigating whether extend can just be implemented as a local heapify.
auto merge of #16667 : retep998/rust/master, r=pcwalton
Add tests.
auto merge of #16675 : luqmana/rust/pmu, r=alexcrichton

Fixes #16671.
Fix intptr_t on win64
Remove stage0 attributes.
Complete renaming of win32 to windows