librustc: Terminate name searches at the nearest module scope for paths that contain at least two components. r=graydon

librustc: Implement explicit self for Add and Index; add a hack in the borrow checker to support this. r=nmatsakis

and re-register snapshots

Just removing unneeded code, no review

This reverts commit ac50046a.

parse_item_or_view_item() would drop visibility if none of the conditions
following it would hold. This was the case when parsing extern {} blocks,
where the function was only used to parse view items, but discarded the
visibility of the first not-view item.

This is built on top of the existing functionality, but
adds a `groups` module which defines functions allowing
the user to specify whole short/long/description groups
at once and provides a usage message.

Two separate changes that got intertwined (sorry):

Make to_str pure. Closes #3691

In str, change functions like push_char to take an &mut str instead of
an &str. Closes #3710

Sadly, there's only one file that requires deprecated modes
(stackwalk)... So, forbid them everywhere else.

This removes most explicit uses of the + argument mode. Pending a
snapshot, I had to remove the forbid(deprecated_modes) pragma from
a bunch of files. I'll put it back!

+ mode still has to be used in a few places for functions that get
moved (see task.rs)

The changes outside core and std are due to the to_bytes trait and
making the compiler (with legacy modes on) agree with the libraries
(with legacy modes off) about modes.

This matches the str::raw function.

Everything should now call ptr::addr_of instead of
ptr::p2::addr_of. Only the pipes macro code when compiled
by stage0 will call ptr::p2::addr_of. Needs a snapshot to get
rid of that.

Currently, the new version is ptr::p2::addr_of and the old one is
ptr::addr_of. This is kind of cheesy, but I need a snapshot before I
can ditch the old version, since the pipe compiler generates calls to
addr_of.

core is converted over to use the new version, std is not.