core: Remove pipes::spawn_service, spawn_service_recv

These are only used in test cases; pipes isn't the right place for them;
they are unnecessary.

Conflicts:
	src/libcore/rt/uv/mod.rs
core: Just reordering some code
core: Remove #[doc(hidden)] attributes and atomic wrapper functions from pipes

Neither are needed
core: Inline the protocol definitions of sendp and oneshot

I want to be able to see what is going on
core: Remove a stray #[doc(hidden)] attribute
core::comm: Remove functions in favor of methods

`send`, etc. are never used. I've left the functions for oneshot pipes
because by-value methods don't work.
core::pipes: Just reordering declarations
core::comm: Modernize constructors to use `new`