std::rand: correct an off-by-one in the Ziggurat code.

The code was using (in the notation of Doornik 2005) `f(x_{i+1}) -
f(x_{i+2})` rather than `f(x_i) - f(x_{i+1})`. This corrects that, and
removes the F_DIFF tables which caused this problem in the first place.

They `F_DIFF` tables are a micro-optimisation (in theory, they could
easily be a micro-pessimisation): that `if` gets hit about 1% of the
time for Exp/Normal, and the rest of the condition involves RNG calls
and a floating point `exp`, so it is unlikely that saving a single FP
subtraction will be very useful (especially as more tables means more
memory reads and higher cache pressure, as well as taking up space in
the binary (although only ~2k in this case)).

Closes #10084. Notably, unlike that issue suggests, this wasn't a
problem with the Exp tables. It affected Normal too, but since it is
symmetric, there was no bias in the mean (as the bias was equal on the
positive and negative sides and so cancelled out) but it was visible as
a variance slightly lower than it should be.
fix missing_doc lint on private traits

Fixes #10069.
add target triple arm-apple-darwin
Declare all Rust functions as unnamed_addr. Closes #8957
Fix infinite recursion in `fill_bytes()`

Fix the implementation of `std::rand::Rng::fill_bytes()` for
`std::rand::reseeding::ReseedingRng` to call the `fill_bytes()` method
of the underlying RNG rather than itself, which causes infinite
recursion.

Fixes #10202.
Name the rustc task 'rustc'
Reduce the aggressiveness of reachability

Previously, all functions called by a reachable function were considered
reachable, but this is only the case if the original function was possibly
inlineable (if it's type generic or #[inline]-flagged).
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).
Drop struct fields if the user destructor fails

This commit changes drop glue generated for structs to use the invoke LLVM
instruction instead of call. What this means is that if the user destructor
triggers an unwinding, then the fields of the struct will still ge dropped.

This is not an attempt to support failing while failing, as that's mostly a
problem of runtime support. This is more of an issue of soundness in making sure
that destructors are appropriately run. The test included fails before this
commit, and only has one call to fail!(), yet it doesn't destroy its struct
fields.
configure: Fix passing multiple target and host triples.
auto merge of #10196 : huonw/rust/fix-zig, r=alexcrichton

The code was using (in the notation of Doornik 2005) `f(x_{i+1}) -
f(x_{i+2})` rather than `f(x_i) - f(x_{i+1})`. This corrects that, and
removes the F_DIFF tables which caused this problem in the first place.

They `F_DIFF` tables are a micro-optimisation (in theory, they could
easily be a micro-pessimisation): that `if` gets hit about 1% of the
time for Exp/Normal, and the rest of the condition involves RNG calls
and a floating point `exp`, so it is unlikely that saving a single FP
subtraction will be very useful (especially as more tables means more
memory reads and higher cache pressure, as well as taking up space in
the binary (although only ~2k in this case)).

Closes #10084. Notably, unlike that issue suggests, this wasn't a
problem with the Exp tables. It affected Normal too, but since it is
symmetric, there was no bias in the mean (as the bias was equal on the
positive and negative sides and so cancelled out) but it was visible as
a variance slightly lower than it should be.

New plot:

![exp-density](https://f.cloud.github.com/assets/1203825/1445796/42218dfe-422a-11e3-9f98-2cd146b82b46.png)

I've started writing some tests in [huonw/random-tests](https://github.com/huonw/random-tests) (not in the main repo because they can and do fail occasionally, due to randomness, but it is on Travis and Rust-CI so it will hopefully track the language), unsurprisingly, they're [currently failing](https://travis-ci.org/huonw/random-tests/builds/13313987) (note that both exp and norm are failing, the former due to both mean and variance the latter due to just variance), but pass at the 0.01 level reliably with this change.

(Currently the only test is essentially a quantitative version of the plots I've been showing, which is run on the `f64` `Rand` instance (uniform 0 to 1), and the Normal and Exp distributions.)
auto merge of #10203 : kud1ing/rust/ios, r=alexcrichton

This is based on the work by @dobkeratops, updated and extended to work for Xcode 5.

This gets you going. I will add separate PRs for compilation/linking fixes.
See also https://github.com/mozilla/rust/wiki/Doc-building-for-ios
std::rand: Move distributions to a subfolder.
auto merge of #10205 : brson/rust/unnamed_addr, r=thestinger
std::rand: Implement the Gamma distribution.
std::rand: share the benchmark counter among the whole module tree.
auto merge of #10213 : telotortium/rust/rand-fill_bytes-stack-overflow, r=huonw

Fix the implementation of `std::rand::Rng::fill_bytes()` for
`std::rand::reseeding::ReseedingRng` to call the `fill_bytes()` method
of the underlying RNG rather than itself, which causes infinite
recursion.

Fixes #10202.
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