Remove resolve's xray infrastructure

Since the removal of privacy from resolve, this flag is no longer necessary to
get the test runner working. All of the privacy checks are bypassed by a special
item attribute in the privacy visitor.

Closes #4947
Move std::rt::io to std::io
rt: Delete more C++
auto merge of #10439 : brson/rust/rmcxx, r=bstrie
Improve error message for breaks in blocks

Before it was always stated that it was a "break outside of a loop" when you
could very well be in a loop, but just in a block instead.

Closes #3064
auto merge of #10423 : alexcrichton/rust/move-io, r=pcwalton

I still plan on reorganizing the internals of the IO module a bit, but this is the major move which has been on the horizon for awhile.
auto merge of #10427 : alexcrichton/rust/no-xray, r=brson

Just a few triage issues that I ran into.
Fixed xfail for nbody shootout benchmark by correcting command line parse.
Cleaned up unneeded imports and type changes to resolve compiler warnings.
auto merge of #10410 : willingc/rust/shoot-done, r=huonw

...e.

Cleaned up unneeded imports and type changes to resolve compiler warnings.

Work in process
rustpkg: Eliminate the spurious `os::path_exists(&pkg_src.start_dir.join(p))` assertion failure

This addresses the problem reported in #10253 and possibly elsewhere.

Closes #10253
auto merge of #10342 : catamorphism/rust/rustpkg-dir-checking-and-monitor, r=erickt

r? @brson
io: benchmarks for creation of the various Buffered objects
auto merge of #10441 : cmr/rust/bench_bufferedstream, r=alexcrichton

https://github.com/mozilla/rust/pull/10424 did optimizations without adding a
way to measure their effect and ensure no regressions. This fixes that.