r?
This pull request is a grab bag of work on the new scheduler.
The most important commit here is where I [outline](https://github.com/brson/rust/blob/io/src/libcore/rt/io/mod.rs) a fairly complete I/O API, based on `Reader` and `Writer` types, as in the current `core::io` module. I've organized this version into a number of modules with declarations for Files, TCP, UDP, Unix sockets, blocking/non-blocking implementations, memory buffers, compression adapters. I'm trying to get this into shape to present on the mailing list.
This branch also wires up `spawn` to the new scheduler, and simplifies the core scheduler operations.
It will check which scheduler it is running under and create the
correct type of task as appropriate. Most options aren't supported
but basic spawning works.
This adds debugging symbol generation for boxes, bare functions, vectors, and strings, along with a tests for boxes and vectors.
Note that gdb will see them as their actual compiled representation with the refcount, tydesc, etc. fields, so if `b` refers to box, `b->boxed` will refer to its value. Also, since you seem to use the [C struct hack](http://c-faq.com/struct/structhack.html) for dynamic vectors, you won't be able to print out the whole vector at once, only one element at a time by indexing specific elements.
The documentation was unclear/wrong: it implies the functions operated on unicode char indices, but they actually operate on byte indices. Also, the `char_at_reverse` documentation was unclear whether it counted from the beginning or the end (causing #5956).
This builds on #5909. I've been combing through the pipes code to understand it and started refactoring a bit.
* Removes pipes::spawn_* functions. These are not particularly useful since they deal with low-level pipes types.
* Inlines the protocol-compiled definitions of `oneshot` and `streamp`. These are the only two uses of the protocol compiler in core and I'm inlining them so I can understand what they are doing as I work on pipes. I may un-inline them in the future.
* Removes redundant functions from core::comm
* Change the constructors to use the `new` convention
Like I commented in #2043, I can't reproduce the weirdness from #1388 on either mac or linux (x84_64) and pushing to try gives all green.
That's 128 less bytes to have to keep in the stack for every call to __morestack.
