Rename {Reader,Writer}ByteConversions methods

The method names in std::rt::io::extensions::WriterByteConversions are
the same as those in std::io::WriterUtils and a resolve error causes
rustc to fail after trying to find an impl of io::Writer instead of
trying to look for rt::io::Writer as well.

Same goes for ReaderByteConversions.
Fix some vector function failure tests. Closes #8698
test: add support for sharding testsuite by passing --test-shard=a.b
Talk about trait bounds in the tutorial.
Document the task watching / exit code propagation implementation.
std: Reduce TLS access
Define cfg(rtopt) when optimizing. Turn off runtime sanity checks

Naturally, and sadly, turning off sanity checks in the runtime is
a noticable performance win. The particular test I'm running goes from
~1.5 s to ~1.3s.

Sanity checks are turned *on* when not optimizing, or when cfg
includes `rtdebug` or `rtassert`.
std: Convert some assert!s to rtassert!
Add new function str.truncate()
auto merge of #8722 : graydon/rust/2013-08-23-test-shard, r=msullivan

This makes it relatively easy for us to split testsuite load between machines in buildbot. I've added buildbot-side support for setting up builders with -a.b suffixes (eg. linux-64-opt-vg-0.5, linux-64-opt-vg-1.5, linux-64-opt-vg-2.5, linux-64-opt-vg-3.5, linux-64-opt-vg-4.5 causes the valgrind-supervised testsuite to split 5 ways across hosts).
auto merge of #8679 : singingboyo/rust/json-to-impl, r=alexcrichton

to_str, to_pretty_str, to_writer, and to_pretty_writer were at the top
level of extra::json, this moves them into an impl for Json to match
with what's been done for the rest of libextra and libstd.  (or at least for vec and str)

Also meant changing some tests.

Closes #8676.
auto merge of #8725 : bblum/rust/docs, r=graydon

This documents how to use trait bounds in a (hopefully) user-friendly way, in the containers tutorial, and also documents the task watching implementation for runtime developers in kill.rs.

r anybody
rustllvm: Specify hard floats for gnueabihf.
auto merge of #8732 : kballard/rust/str-truncate, r=thestinger
Force line ending of '.in' files in jemalloc to LF

This fixes issue #8731 . On Windows, if the git option core.autocrlf is true (github recommends users to turn on this flag - see https://help.github.com/articles/dealing-with-line-endings), the headers generated from the .in files will have syntatic errors, causing compilation to fail.
librustc: Always use session target triple.
Merge pull request #8738 from mukilan/master

Force line ending of '.in' files in jemalloc to LF
Remove ifmt hax and implement fprintf
Implement a wrapper macro around fprintf -- ifmtf
Settle on the format/write/print family of names