native, rustuv: Fix spawning with empty args

There was a bug in both libnative and libuv which prevented child processes from
being spawned correctly on windows when one of the arguments was an empty
string. The libuv bug has since been fixed upstream, and the libnative bug was
fixed as part of this commit.

When updating libuv, this also includes a fix for #15149.

Closes #15149
Closes #16272
API docs/examples for std::slice

 - API doc/example for next() in Permutations
 - API doc/example for permutations() in ImmutableCloneableVector
 - Moved examples for permutations and next into trait definition as
   comments on pull request #16244.
 - Fix erroneus inclusion of src/llvm in older commit.
Update docs to use HTTPS for static.rust-lang.org addresses

cc #16123
Download snapshots using HTTPS

cc #16123
auto merge of #16427 : brson/rust/https, r=thestinger
auto merge of #16417 : jasonthompson/rust/docs/slice3, r=alexcrichton

- Moved examples for permutations and next into trait definition as
   comments on pull request #16244.
- Fixed (hopefully) issue with erronious commit of changes to src/llvm.
auto merge of #16284 : alexcrichton/rust/issue-16272, r=aturon

There was a bug in both libnative and libuv which prevented child processes from
being spawned correctly on windows when one of the arguments was an empty
string. The libuv bug has since been fixed upstream, and the libnative bug was
fixed as part of this commit.

When updating libuv, this also includes a fix for #15149.

Closes #15149
Closes #16272
Deprecate and rename Option/Result methods to match new conventions

The details of the new conventions can be found on discuss:

    http://discuss.rust-lang.org/t/settling-some-key-naming-conventions/269/35

and in the guidelines:

    http://aturon.github.io/style/naming/README.html

This is a:

[breaking-change]
Deprecate/rename BitvSet methods to match new conventions

The details of the new conventions can be found on discuss:

    http://discuss.rust-lang.org/t/settling-some-key-naming-conventions/269/35

and in the guidelines:

    http://aturon.github.io/style/naming/README.html

This is a:

[breaking-change]
Deprecate/rename methods for Terminal trait to
match new conventions

The details of the new conventions can be found on discuss:

    http://discuss.rust-lang.org/t/settling-some-key-naming-conventions/269/35

and in the guidelines:

    http://aturon.github.io/style/naming/README.html

This is a:

[breaking-change]
Deprecate and rename iterators and mut_ prefixes.

The details of the new conventions can be found on discuss:

    http://discuss.rust-lang.org/t/settling-some-key-naming-conventions/269/35

and in the guidelines:

    http://aturon.github.io/style/naming/README.html

This is a:

[breaking-change]
Fallout from iterators and mut_ prefixes
Rename uses of unwrap and friends