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.

Also, allow let bindings in a block to shadow each other.

Fails consistently on windows

Trying to shutdown cleanly results in wierd failures

Now, llvm probably won't actually *emit* a tail call with the compiler
options and configuration we have, but this should punt it over to the
more general "do tail calls" bug.

Seems to be failing with some consistency