This builds on https://github.com/rust-lang/rust/pull/17109, putting the target triple into the installer name so that we can have both 32-bit and 64-bit.

The resulting installers will be called `rust-0.12.0-pre-x86_64-w64-mingw32.exe`, etc.

This adds links to SO, reddit, and discuss to the README. The main intent is to start advertising discuss.rust-lang.org more, in a location that doesn't mislead casual users to it (people who are building Rust are more likely to be the right audience than those that are just visiting the web site).

Currently `./configure --llvm-root=...` and similar flags will break incremental builds by forcing reconfiguration on every `make`.  This happens because `reconfig.mk` incorrectly treats submodules in the `-` (uninitialized) state as requiring reconfiguration, and `./configure` deliberately deinitializes unneeded submodules.  The fix is to reconfigure only when submodules are in the `+` state (wrong commit checked out).

Previously, some parts of this optimization were impossible because the
alignment passed to the free function was not correct. That was fully
fixed by #17012.

Closes #17092

Closes #13994

Previously, some parts of this optimization were impossible because the
alignment passed to the free function was not correct. That was fully
fixed by #17012.

Closes #17092

I missed some annotations, and some were in a different style.

Instead of `extern crate foo = bar`, write `extern crate bar as foo`.
Instead of `extern crate baz = "quux"`, write `extern crate "quux" as
baz`.

Closes #16461.

[breaking-change]

r? @brson

A few steps toward https://github.com/rust-lang/rust/issues/15994

Instead of `extern crate foo = bar`, write `extern crate bar as foo`.
Instead of `extern crate baz = "quux"`, write `extern crate "quux" as
baz`.

Closes #16461.

[breaking-change]

Based on an observation that strings and arguments are always interleaved, thanks to #15832. Additionally optimize invocations where formatting parameters are unspecified for all arguments, e.g. `"{} {:?} {:x}"`, by emptying the `__STATIC_FMTARGS` array. Next, `Arguments::new` replaces an empty slice with `None` so that passing empty `__STATIC_FMTARGS` generates slightly less machine code when `Arguments::new` is inlined. Furthermore, formatting itself treats these cases separately without making redundant copies of formatting parameters.

All in all, this adds a single mov instruction per `write!` in most cases. That's why code size has increased.

I missed some annotations, and some were in a different style.

Format specs are ignored and not stored in case they're all default.
Restore default formatting parameters during iteration.
Pass `None` instead of empty slices of format specs to take advantage
of non-nullable pointer optimization.

Generate a call to one of two functions of `fmt::Argument`.