convert doc-attributes to doc-comments using ./src/etc/sugarise-doc-comments.py (and manually tweaking) - for issue #2498

also whitespace cleanup

.. for now, the test just spins up the server and listens for messages,
echoing them back to an output port. there's a "kill" msg that it will
listen for. need to point the tcp client and server test impls at each
other for a loopback server/client test, like how its done in uv::ll

once ipv6 parse/format lands, i can add another test using the entirely
same codebase, but substituting an ip_addr ipv6 varient for the ipv4
varient used in the existing code

still need some other plumbing to get the client/server tests to work
together.

Issue #2111

So that they can be used with user input without causing task
failures.

Closes #1335

* Renamed str::split -> str::split_byte
* Renamed str::splitn -> str::splitn_byte
* Renamed str::split_func -> str::split
* Renamed str::split_char -> str::split_char
* Renamed str::split_chars_iter -> str::split_char_iter
* Added u8::is_ascii
* Fixed the behavior of str::split_str, so that it matches split_chars
  and split (i.e. ["", "XXX", "YYY", ""] == split_str(".XXX.YYY.", "."))
* Fixed str::split_byte and str::splitn_byte so that they handle
  splitting UTF-8 strings on a given UTF-8/ASCII byte and also handle ""
  as the others do

Long lines were fixed in a very crude way, as I'll be following up
with another reformat in a bit.

This changes the indexing syntax from .() to [], the vector syntax from ~[] to
[] and the extension syntax from #fmt() to #fmt[]

Removed trans_comm.rs from the compiler. Updating aio/sio to work with the new chan and port system, started on a networking module for the standard library.