Implemented Decodable/Encodable for Cell and RefCell. Fixes #15395

Updated PR with fixme and test

Updated PR with fixme and test
auto merge of #15411 : mitchmindtree/rust/master, r=alexcrichton

I ran `make check` and everything went smoothly. I also tested `#[deriving(Decodable, Encodable)]` on a struct containing both Cell<T> and RefCell<T> and everything now seems to work fine.
manual: Fix typo.

Also removes redundant newline in code block.
auto merge of #15489 : jakub-/rust/issue-15488, r=pcwalton

Fixes #15488.
auto merge of #15496 : ruud-v-a/rust/patch-1, r=huonw

Also removes redundant newline in code block.
Add example for str replace() and MaybeOwned

  - for 3 implementations of into_maybe_owned()
  - is_slice()
  - is_owned()
collections: flesh out the Vec::clone_from benchmarks to cover reuse
collections: minimize code that's in unsafe blocks

This changes Vec::from_slice to call unsafe_push_all_clone
directly to avoid doing an unnecessary reserve_additional call
collections: merge unsafe_push_all_clone and push_all
Strip empty strings from link args

Closes #15487
auto merge of #15502 : sfackler/rust/link_args_spaces, r=alexcrichton

Closes #15487
librustc: Disallow modules and types from having the same name.

This will break code that looks like:

    struct Foo {
        ...
    }

    mod Foo {
        ...
    }

Change this code to:

    struct Foo {
        ...
    }

    impl Foo {
        ...
    }

Or rename the module.

Closes #15205.

[breaking-change]
librustc (RFC #34): Implement the new `Index` and `IndexMut` traits.

This will break code that used the old `Index` trait. Change this code
to use the new `Index` traits. For reference, here are their signatures:

    pub trait Index<Index,Result> {
        fn index<'a>(&'a self, index: &Index) -> &'a Result;
    }
    pub trait IndexMut<Index,Result> {
        fn index_mut<'a>(&'a mut self, index: &Index) -> &'a mut Result;
    }

Closes #6515.

[breaking-change]
Add libunicode; move unicode functions from core

- created new crate, libunicode, below libstd
- split Char trait into Char (libcore) and UnicodeChar (libunicode)
  - Unicode-aware functions now live in libunicode
    - is_alphabetic, is_XID_start, is_XID_continue, is_lowercase,
      is_uppercase, is_whitespace, is_alphanumeric, is_control,
      is_digit, to_uppercase, to_lowercase
  - added width method in UnicodeChar trait
    - determines printed width of character in columns, or None if it is
      a non-NULL control character
    - takes a boolean argument indicating whether the present context is
      CJK or not (characters with 'A'mbiguous widths are double-wide in
      CJK contexts, single-wide otherwise)
- split StrSlice into StrSlice (libcore) and UnicodeStrSlice
  (libunicode)
  - functionality formerly in StrSlice that relied upon Unicode
    functionality from Char is now in UnicodeStrSlice
    - words, is_whitespace, is_alphanumeric, trim, trim_left, trim_right
  - also moved Words type alias into libunicode because words method is
    in UnicodeStrSlice
- unified Unicode tables from libcollections, libcore, and libregex into
  libunicode
- updated unicode.py in src/etc to generate aforementioned tables
- generated new tables based on latest Unicode data
- added UnicodeChar and UnicodeStrSlice traits to prelude
- libunicode is now the collection point for the std::char module,
  combining the libunicode functionality with the Char functionality
  from libcore
  - thus, moved doc comment for char from core::char to unicode::char
- libcollections remains the collection point for std::str

The Unicode-aware functions that previously lived in the Char and
StrSlice traits are no longer available to programs that only use
libcore. To regain use of these methods, include the libunicode crate
and use the UnicodeChar and/or UnicodeStrSlice traits:

    extern crate unicode;
    use unicode::UnicodeChar;
    use unicode::UnicodeStrSlice;
    use unicode::Words; // if you want to use the words() method

NOTE: this does *not* impact programs that use libstd, since UnicodeChar
and UnicodeStrSlice have been added to the prelude.

closes #15224
[breaking-change]
Improve non-exhaustive pattern witnesses for structs with multiple fields
auto merge of #15440 : pcwalton/rust/struct-aliases, r=brson

Closes #4508.

r? @nick29581
librustc: Update debuginfo.
auto merge of #15394 : pcwalton/rust/new-index-traits, r=nick29581

This will break code that used the old `Index` trait. Change this code
to use the new `Index` traits. For reference, here are their signatures:

    pub trait Index<Index,Result> {
        fn index<'a>(&'a self, index: &Index) -> &'a Result;
    }
    pub trait IndexMut<Index,Result> {
        fn index_mut<'a>(&'a mut self, index: &Index) -> &'a mut Result;
    }

Closes #6515.

[breaking-change]

r? @nick29581
auto merge of #15406 : luqmana/rust/nop, r=pcwalton

Extend the null ptr optimization to work with slices, closures, procs, & trait objects by using the internal pointers as the discriminant.

This decreases the size of `Option<&[int]>` (and similar) by one word.
mk: Run tidy after tests in 'make check'

Tidy takes like forever to run.