std::rt: require known stack bounds for all tasks.

We just approximate with a 1 or 2 MB stack for native::start.
Register new snapshots
stop treating `Rc` cycles as unsafe
add a strong/weak reference counted pointer type
rename Strong -> Rc, replacing `rc` with `weak`
Update doc/po4a.conf for recent changes.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Remove *.pot files and ignore them now.

The .pot files can be generated automatically and the files contain
timestamps in their content. They can cause huge conflicts and take huge
space even if you are not a translator.

This commit is a part of improvement discussed on
https://github.com/mozilla/rust/pull/11383 .

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
auto merge of #11427 : omasanori/rust/remove-pot, r=alexcrichton

`doc/po/*.pot` files are generated automatically using `po4a` and they includes timestamps in their content. The files can cause huge conflicts unnecessarily. Also, removing them save disk space if you are not a translator.
librustc: Implement placement `box` for GC and unique pointers.
auto merge of #11055 : pcwalton/rust/placement-box, r=pcwalton

r? @nikomatsakis
rustc: Fix style of OutputType enum
rustc: Fix style of Lint enum
port over the old tests to the new `Rc`
auto merge of #10926 : thestinger/rust/rc, r=cmr
auto merge of #11360 : huonw/rust/stack_bounds, r=alexcrichton

We just approximate with a 2MB stack for native::start.
Update submodules to point to rust-lang repos
Add eof to MemReader and BufReader

It's easy to figure out and useful as a sanity check sometimes.
auto merge of #11418 : alexcrichton/rust/snapshots, r=cmr
Fix ICE on const of nullable enum with fields in null case.

That is, if you have an enum type that is subject to the nullable
pointer optimization, but the null variant has a nonzero number of
fields, and you declare a static whose value is of that variant, then
that used to be an ICE but this change fixes it.
auto merge of #11433 : brson/rust/minorstylefixes, r=alexcrichton