Followup to PR #16477: a run-pass regression test for Issue #15750.
Add a test for complex divide by zero.
Add export_name to the attribute whitelist and a description in the rust manual
librustc: Don't create scratch for the base expr in function record update.
librustc: Fix trans for functional record update when discarding the result.
std::io::util cleanup + fixes

* Fix `LimitReader`'s `Buffer::consume` impl to avoid limit underflow
* Make `MultiWriter` fail fast instead of always running through each
    `Writer`. This may or may not be what we want, but it at least
    doesn't throw any errors encountered in later `Writer`s into oblivion.
* Prevent `IterReader`'s `Reader::read` impl from returning EOF if given
    an empty buffer.

[breaking-change]
auto merge of #16494 : pnkfelix/rust/fsk-quotstx-followup, r=alexcrichton

Followup to PR #16477: a run-pass regression test for Issue #15750.
Generate slightly better unoptimized code for for-loops

The discriminant for Option values is either 0 or 1, so we can just
truncate the value to an i1, which ends up as a no-op for Options
containing pointers.
auto merge of #16500 : jackheizer/rust/export-name, r=alexcrichton
debuginfo: Add a "no_debug" attribute that allows to exclude functions from debuginfo generation.
auto merge of #16497 : michaelwoerister/rust/no_debug_attribute, r=pcwalton

Fixes #15332.
Fix builds with LLVM < 3.6
Derive Clone for std::time::Duration

This is needed to derive Clone for types containing Durations.
auto merge of #16511 : luqmana/rust/sbnt, r=pcwalton

Fixes #15397.
Fixes #7261.
Fixes #6573.
mark &T params without UnsafeCell<U> as readonly

These are already marked as `noalias` due to the immutability guarantee
(see 4c2d4cd3dea344e81e4df24382ac3f23e2f86f40), but more information can
be bubbled up to the caller via `readonly`.
auto merge of #16517 : dotdash/rust/for_trunc, r=pcwalton

The discriminant for Option values is either 0 or 1, so we can just
truncate the value to an i1, which ends up as a no-op for Options
containing pointers.
Fix the order in which struct fields drop

When a struct implements Drop, its fields should still drop in
declaration order (just as they do when the struct does not implement
Drop).

Fixes #16492.
auto merge of #16493 : kballard/rust/fix_drop_field_order, r=pnkfelix

When a struct implements Drop, its fields should still drop in
declaration order (just as they do when the struct does not implement
Drop).

Fixes #16492.
vim: Don't set foldmethod in the syntax file either

We shouldn't be setting any settings in the syntax file. Better to put
them in the ftplugin, where they won't be pulled in by :syn-include and
can be cleaned up when changing the filetype.
auto merge of #16519 : apoelstra/rust/patch-1, r=alexcrichton

This is needed to derive Clone on structures containing durations.