syntax: Tighten search paths for inner modules

This is an implementation of RFC 16. A module can now only be loaded if the
module declaring `mod name;` "owns" the current directory. A module is
considered as owning its directory if it meets one of the following criteria:

* It is the top-level crate file
* It is a `mod.rs` file
* It was loaded via `#[path]`
* It was loaded via `include!`
* The module was declared via an inline `mod foo { ... }` statement

For example, this directory structure is now invalid

    // lib.rs
    mod foo;

    // foo.rs
    mod bar;

    // bar.rs;
    fn bar() {}

With this change `foo.rs` must be renamed to `foo/mod.rs`, and `bar.rs` must be
renamed to `foo/bar.rs`. This makes it clear that `bar` is a submodule of `foo`,
and can only be accessed through `foo`.

RFC: 0016-module-file-system-hierarchy
Closes #14180

[breaking-change]
Replaced Ord by TotalOrd in priority queue
Rename to_vec and to_sorted_vec
Refactored and renamed functions to avoid failure
Fix dead code warnings
Fix insert_ordered in DList
auto merge of #14251 : alexcrichton/rust/hierarchy, r=huonw

This is an implementation of RFC 16. A module can now only be loaded if the
module declaring `mod name;` "owns" the current directory. A module is
considered as owning its directory if it meets one of the following criteria:

* It is the top-level crate file
* It is a `mod.rs` file
* It was loaded via `#[path]`
* It was loaded via `include!`
* The module was declared via an inline `mod foo { ... }` statement

For example, this directory structure is now invalid

    // lib.rs
    mod foo;

    // foo.rs
    mod bar;

    // bar.rs;
    fn bar() {}

With this change `foo.rs` must be renamed to `foo/mod.rs`, and `bar.rs` must be
renamed to `foo/bar.rs`. This makes it clear that `bar` is a submodule of `foo`,
and can only be accessed through `foo`.

RFC: 0016-module-file-system-hierarchy
Closes #14180

[breaking-change]
Minor doc fixes in various places
auto merge of #14279 : aochagavia/rust/pr2, r=huonw

The breaking changes are:

* Changed `DList::insert_ordered` to use `TotalOrd`, not `Ord`
* Changed `PriorityQueue` to use `TotalOrd`, not `Ord`
* Deprecated `PriorityQueue::maybe_top()` (renamed to replace `PriorityQueue::top()`)
* Deprecated `PriorityQueue::maybe_pop()` (renamed to replace `PriorityQueue::pop()`)
* Deprecated `PriorityQueue::to_vec()` (renamed to `PriorityQueue::into_vec()`)
* Deprecated `PriorityQueue::to_sorted_vec()` (renamed to `PriorityQueue::into_sorted_vec()`)
* Changed `PriorityQueue::replace(...)` to return an `Option<T>` instead of failing when the queue is empty.


[breaking-change]
Fix typo in libcore
auto merge of #14291 : Sawyer47/rust/doc-fixes, r=alexcrichton
auto merge of #14292 : limeburst/rust/master, r=alexcrichton
Rename Result.unwrap_or_handle() to .unwrap_or_else()

Result.unwrap_or_handle() is the equivalent of Option.unwrap_or_else().
In the interests of naming consistency, call it the same thing.

[breaking-change]
auto merge of #14294 : kballard/rust/result_unwrap_or_else, r=alexcrichton

Result.unwrap_or_handle() is the equivalent of Option.unwrap_or_else().
In the interests of naming consistency, call it the same thing.

[breaking-change]
libcollections: remove `init_to_vec`

The `init_to_vec` function in `collections::bitv` was exposed as an
inherent method, but appears to just be a helper function for the
`to_vec` method. This patch inlines the definition, removing
`init_to_vec` from the public API.

[breaking-change]
test: index shards at 1, not 0

This has no tests because it's near impossible to test -- since TestFn uses
`proc`s, they can not be cloned or tested for equality. The only way to really
test this is making sure that for a given number of shards `a`, sharding from
1 to `a` yields the complete set of tests. But `filter_tests` takes its vector
by value and `proc`s cannot be compared.

[breaking-change]

Closes #10898
auto merge of #14286 : cmr/rust/shard-benches, r=alexcrichton

This has no tests because it's near impossible to test -- since TestFn uses
`proc`s, they can not be cloned or tested for equality. The only way to really
test this is making sure that for a given number of shards `a`, sharding from
1 to `a` yields the complete set of tests. But `filter_tests` takes its vector
by value and `proc`s cannot be compared.

[breaking-change]

Closes #10898
auto merge of #14295 : aturon/rust/hide-init_to_vec, r=alexcrichton

The `init_to_vec` function in `collections::bitv` was exposed as an
inherent method, but appears to just be a helper function for the
`to_vec` method. This patch inlines the definition, removing
`init_to_vec` from the public API.

[breaking-change]
rustc: Better resolve errors for &T, &mut T, remove failure condition.
core::iter::order functions now take two types of iterators.

Previously the type signatures of the ordering functions in
`core::iter::order` took two iterators, but only if they were
the same type of iterator.  This commit loosens that restriction
and allows different kinds of iterators (but with the same type
of elements) to be compared.