Remove unused imports.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Prefix _ to unused variables.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Append ; to #[allow(dead_code)].

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Add test case for issue #11681
auto merge of #11947 : alexcrichton/rust/osx-unwind, r=brson

On OSX 32-bit, the private fields are 5 words long, not 2. I found this
segfaulting before this change, and after this change it no longer segfaulted.
auto merge of #11918 : omasanori/rust/reduce-warnings, r=alexcrichton

Moving forward to green waterfall.
auto merge of #11929 : FlaPer87/rust/issue-11681, r=huonw

closes #11681
std: Remove io::io_error

* All I/O now returns IoResult<T> = Result<T, IoError>
* All formatting traits now return fmt::Result = IoResult<()>
* The if_ok!() macro was added to libstd
extra: Remove io_error usage
syntax: Remove io_error usage
rustc: Remove io_error usage
compiletest: Remove io_error usage
glob: Remove io_error usage
green: Remove io_error usage
native: Remove io_error usage
rustuv: Remove io_error usage
rustpkg: Remove io_error usage
rustdoc: Remove io_error usage
rpass: Remove io_error usage
std: Fix tests with io_error usage