Document for-loop in tutorial section on loops
 Explain container iteration in the loop tutorial

 As suggested by @pnkfelix in #12161, this extends the examples by a for-loop
 that iterates over a string as an example for container iteration.
Adds support for working with URL Paths

It is sometimes useful to parse just the path portion of a URL (path,
query string and fragment) rather than the entire URL.
mk: Clean up conditions for including dist.mk
mk: Add prepare.mk

This is a slightly more generic rewrite of install.mk. Currently
used for nothing, but we'll base all the binary distributables off it.
mk: Base the install target on prepare.mk
mk: Fix a dist bug

Fallout from moving doc/ to src/doc
mk: Base the windows dist target on prepare.mk
Remove Real trait and move methods into Float

This is part of the effort to simplify `std::num`, as tracked in issue #10387.
Minor documentation fixes in std::fmt

* Change '...your own time' => '...your own type'
* Fix typo in the Vector2D example
Clean up std::task docs, make TaskBuilder a real builder

Delete all the documentation from std::task that references linked
failure.

Tweak TaskBuilder to be more builder-like. .name() is now .named() and
.add_wrapper() is now .with_wrapper(). Remove .watched() and
.unwatched() as they didn't actually do anything.
Update clients of the TaskBuilder API
Allow configuration of uid/gid/detach on processes

This just copies the libuv implementation for libnative which seems reasonable
enough (uid/gid fail on windows).

Closes #12082
Upgrade libuv

This notably includes joyent/libuv@6f62d62c in order to fix when processes fail
to spawn on windows
auto merge of #12085 : alexcrichton/rust/issue-12082, r=brson

This just copies the libuv implementation for libnative which seems reasonable
enough (uid/gid fail on windows).

Closes #12082
Address review feedback
Implement Unix domain sockets in libnative
Move unix pipes implementation to pipe_unix.rs

The windows named pipes implementation will have almost nothing to do with unix
pipes, so I think it's best if they live in separate files.
Implement named pipes for windows, touch up unix

* Implementation of pipe_win32 filled out for libnative
* Reorganize pipes to be clone-able
* Fix a few file descriptor leaks on error
* Factor out some common code into shared functions
* Make use of the if_ok!() macro for less indentation

Closes #11201
Rename Bitwise::population_count to Bitwise::count_ones and add Bitwise::count_zeros

These are inspired by the [functions in the Julia standard library](http://docs.julialang.org/en/release-0.2/stdlib/base/#Base.count_ones).