There were several old `#[doc(hidden)]` attributes in libstd and
libextra, left over from when rustdoc didn't hide private
definitions, tagged with `FIXME #3538`.
Since #3538 is now closed, I removed the `#[doc(hidden)]` attributes
as well as the FIXMEs, but I left `#[doc(hidden)]` in
libstd/task/spawn.rs and libstd/task/rt.rs since those two are
apparently `pub`, as well as in libextra/std.rc since std/extra is
`pub`.
mentioned in #2625.
This change makes the module more oriented around
Process values instead of having to deal with process ids
directly.
Apart from issues mentioned in #2625, other changes include:
- Changing the naming to be more consistent - Process/process
is now used instead of a mixture of Program/program and
Process/process.
- More docs/tests.
Some io/scheduler related issues remain (mentioned in #2625).
