auto merge of #6664 : catamorphism/rust/issue-3796, r=catamorphism
auto merge of #6665 : catamorphism/rust/issue-5741, r=nikomatsakis

r? @nikomatsakis The way we deal with unreachable expressions in trans is pretty ad hoc,
but this at least doesn't make it worse, and eliminates the LLVM
assertion failure reported in #5741.
fix arm stack alignment
auto merge of #6667 : crabtw/rust/arm-rt, r=brson

This fixes segmentation fault of new rt tests.
For example
```
use core::rt::test::*;
use core::rt::comm::*;
use core::cell::Cell;

fn main() {
    do run_in_newsched_task {
        let (port, chan) = oneshot::<~int>();
        let port_cell = Cell(port);
        do spawntask_immediately {
            assert!(port_cell.take().recv() == ~10);
        }
        chan.send(~10);
    }
}
```
"Type :help for help", similar to ghci
Fix #6342
auto merge of #6671 : kud1ing/rust/patch-1, r=z0w0
Implement static_assert attribute

This verifies that a static item evaluates to true, at compile time.
Add static_assert doc blurb
auto merge of #6670 : cmr/rust/static_assert, r=graydon

This verifies that a static item evaluates to true, at compile time.
auto merge of #6672 : yjh0502/rust/fix_6342, r=graydon

Fix #6342
core: Fail with a better error message when list_dir gets an empty path

(Yes, this did happen in real life...)