Name the rustc task 'rustc'
Provide a sound method of flushing stdout

The previous method was unsound because you could very easily create two mutable
pointers which alias the same location (not sound behavior). This hides the
function which does so and then exports an explicit flush() function (with
documentation about how it works).
configure: Fix passing multiple target and host triples.
std::rand: Move distributions to a subfolder.
std::rand: Implement the Gamma distribution.
std::rand: share the benchmark counter among the whole module tree.
Reordered the methods in std::Option and std::Result

Cleaned up the source in a few places

Renamed `map_move` to `map`, removed other `map` methods

Added `as_ref` and `as_mut` adapters to `Result`

Added `fmt::Default` impl
Cleaned up the option and result module in more detail

Made both types implement more standard traits in a nicer way

Derived more traits
Removed legacy implementations
Fixed unused import warning in tests
auto merge of #10218 : alexcrichton/rust/stdio-flush-safe, r=cmr

The previous method was unsound because you could very easily create two mutable
pointers which alias the same location (not sound behavior). This hides the
function which does so and then exports an explicit flush() function (with
documentation about how it works).
Fix typo in to_digit
Give test and main tasks better names

Tests now have the same name as the test that they're running (to allow for
easier diagnosing of failure sources), and the main task is now specially named
<main> instead of <unnamed>.

Closes #10195
Closes #10073
auto merge of #10119 : Kimundi/rust/option_and_generic, r=alexcrichton

This takes the last reforms on the `Option` type and applies them to `Result` too. For that, I reordered and grouped the functions in both modules, and also did some refactorings:

- Added `as_ref` and `as_mut` adapters to `Result`.
- Renamed `Result::map_move` to `Result::map` (same for `_err` variant), deleted other map functions. 
- Made the `.expect()` methods be generic over anything you can
  fail with.
- Updated some doc comments to the line doc comment style
- Cleaned up and extended standard trait implementations on `Option` and `Result`
- Removed legacy implementations in the `option` and `result` module
configure: Remove legacy triple flags.
auto merge of #10204 : alexcrichton/rust/better-names, r=brson

Tests now have the same name as the test that they're running (to allow for
easier diagnosing of failure sources), and the main task is now specially named
`<main>` instead of `<unnamed>`.

Closes #10195
Closes #10073
auto merge of #10220 : luqmana/rust/con, r=brson

Previously we were actually overwriting `CFG_{HOST,TARGET,BUILD}` with `CFG_{HOST,TARGET,BUILD}_TRIPLE(S)` since configure tested for the legacy one by checking if it was empty which would never be the case. That meant it wouldn't split up multiple triples and just treat it as one long triple.

This pull also fixes the rules that were changed when librustuv was added to use the right CFG_ vars and removes the legacy flags.
Bump required pandoc version to 1.9.

Earlier versions of pandoc don't have the default.html5 and thus,
building the docs fail.

Signed-off-by: Noufal Ibrahim <noufal@nibrahim.net.in>
auto merge of #10215 : brson/rust/rustctask, r=thestinger
auto merge of #10223 : huonw/rust/gamma, r=cmr

Implements the [Gamma distribution](https://en.wikipedia.org/wiki/Gamma_distribution), using the algorithm described by Marsaglia & Tsang 2000[1]. I added tests checking that the mean and variance of this implementation is as expected for a range of values of the parameters in https://github.com/huonw/random-tests/commit/5d87c00a0fb69c8fa173593714cef76ddfddb651 (they pass locally, but obviously won't even build on Travis until this is merged).

Also, moves `std::rand::distributions` to a subfolder, and performs a minor clean-up of the benchmarking (makes the number of iterations shared by the whole `std::rand` subtree).

[1]: George Marsaglia and Wai Wan Tsang. 2000. "A Simple Method for Generating Gamma Variables" *ACM Trans. Math. Softw.* 26, 3 (September 2000), 363-372. DOI:[10.1145/358407.358414](http://doi.acm.org/10.1145/358407.358414).