Improve error message for lifetimes after type params.

Closes #14303.
Make most lexer errors non-fatal

Most errors that arise in the lexer can be recovered from. This allows
for more than one syntax error to be reported at a time.
core: Finish stabilizing the `mem` module.

* All of the *_val functions have gone from #[unstable] to #[stable]
* The overwrite and zeroed functions have gone from #[unstable] to #[stable]
* The uninit function is now deprecated, replaced by its stable counterpart,
  uninitialized

[breaking-change]
Fixes problems on systems with opaque mutex

On some systems (iOS for example) mutex is represented by
opaque data structure which doesn't play well with simple
data copy. Therefore mutex should be initialized from
magic static value and filled by OS only when it landed RC.
auto merge of #14388 : kballard/rust/nonfatal_lexer_errors, r=alexcrichton

Most errors that arise in the lexer can be recovered from. This allows
for more than one syntax error to be reported at a time.
auto merge of #14389 : Ryman/rust/14303, r=alexcrichton

Closes #14303.
auto merge of #14392 : alexcrichton/rust/mem-updates, r=sfackler

* All of the *_val functions have gone from #[unstable] to #[stable]
* The overwrite and zeroed functions have gone from #[unstable] to #[stable]
* The uninit function is now deprecated, replaced by its stable counterpart,
  uninitialized

[breaking-change]
Rename functions in Ascii

Some functions implemented for the Ascii struct have the same functionality as other functions implemented for the normal chars. For consistency, I think they should have the same name, so I renamed the functions in Ascii to match the names in the Char trait.

* Renamed `to_lower` to `to_lowercase`
* Renamed `to_upper` to `to_uppercase`
* Renamed `is_alpha` to `is_alphabetic`
* Renamed `is_alnum` to `is_alphanumeric`
* Renamed `is_lower` to `is_lowercase`
* Renamed `is_upper` to `is_uppercase`

[breaking-change]
std: minor simplification to sync::deque.
auto merge of #14396 : vhbit/rust/opaque-mutex, r=alexcrichton

On some systems (iOS for example) mutex is represented by opaque data structure which doesn't play well with simple data copy. Therefore mutex should be initialized from magic static value and filled by OS only when it landed RC.

Initially written for iOS but since landing iOS support might require quite a lot of time I think it is better to split parts which aren't directly related to iOS and merge them in
Removed unnecessary macro declaration
auto merge of #14405 : aochagavia/rust/pr5, r=cmr
auto merge of #14378 : huonw/rust/deque-adjustments, r=alexcrichton

Might as well remove the duplication/`forget` call.
Update ascii functions used elsewhere
auto merge of #14401 : aochagavia/rust/pr4, r=alexcrichton

Some functions implemented for the Ascii struct have the same functionality as other functions implemented for the normal chars. For consistency, I think they should have the same name, so I renamed the functions in Ascii to match the names in the Char trait.

* Renamed `to_lower` to `to_lowercase`
* Renamed `to_upper` to `to_uppercase`
* Renamed `is_alpha` to `is_alphabetic`
* Renamed `is_alnum` to `is_alphanumeric`
* Renamed `is_lower` to `is_lowercase`
* Renamed `is_upper` to `is_uppercase`

[breaking-change]
Add AttrId to Attribute_
First sketch of lint pass

Enough attributes are marked to cleanly compile an empty library.
Port more stuff to mark used attributes
Whitelist doc attributes

This is a bit overly permissive but should be okay for now.
Get "make check" to work with unused-attribute

There's a fair number of attributes that have to be whitelisted since
they're either looked for by rustdoc, in trans, or as needed. These can
be cleaned up in the future.