Append missing padding after last field of struct

This patch fixes issue #13186.

When generating constant expression for enum, it is possible that
alignment of expression may be not equal to alignment of type.  In that
case space after last struct field must be padded to match size of value
and size of struct. This commit adds that padding.

See detailed explanation in src/test/run-pass/trans-tag-static-padding.rs
Be more clear about what this lambda expression does
Give more explanation when introducing closures
Demonstrate accessing external variable in first example
Some more closure changes
Apply lint attrs to individual "use" declarations

Fixes #10534
Register new snapshots

These are the first successful snapshots after the LLVM upgrade, built with LLVM
that requires C++11
native: Remove unused and untested UnixDatagram
std: Add timeouts to unix connect/accept

This adds support for connecting to a unix socket with a timeout (a named pipe
on windows), and accepting a connection with a timeout. The goal is to bring
unix pipes/named sockets back in line with TCP support for timeouts.

Similarly to the TCP sockets, all methods are marked #[experimental] due to
uncertainty about the type of the timeout argument.

This internally involved a good bit of refactoring to share as much code as
possible between TCP servers and pipe servers, but the core implementation did
not change drastically as part of this commit.

cc #13523
use option_env! instead of env!
Pre-step towards issue #12624 and others: Introduce ExprUseVisitor, remove the
moves computation. ExprUseVisitor is a visitor that walks the AST for a
function and calls a delegate to inform it where borrows, copies, and moves
occur.

In this patch, I rewrite the gather_loans visitor to use ExprUseVisitor, but in
future patches, I think we could rewrite regionck, check_loans, and possibly
other passes to use it as well. This would refactor the repeated code between
those places that tries to determine where copies/moves/etc occur.
Convert delegate to use an object type and remove FIXME from closed issue
add min_pos_value constant for floats

Follow-up on issue #13297 and PR #13710.  Instead of following the (confusing) C/C++ approach
of using `MIN_VALUE` for the smallest *positive* number, we introduce `MIN_POS_VALUE` (and
in the Float trait, `min_pos_value`) to represent this number.

This patch also removes a few remaining redundantly-defined constants that were missed last
time around.
auto merge of #13671 : dcrewi/rust/lint-directives-on-use-items, r=alexcrichton

Fixes #10534
auto merge of #13711 : alexcrichton/rust/snapshots, r=brson

These are the first successful snapshots after the LLVM upgrade, built with LLVM
that requires C++11
auto merge of #13723 : alexcrichton/rust/pipe-connect-timeout, r=brson

This adds support for connecting to a unix socket with a timeout (a named pipe
on windows), and accepting a connection with a timeout. The goal is to bring
unix pipes/named sockets back in line with TCP support for timeouts.

Similarly to the TCP sockets, all methods are marked #[experimental] due to
uncertainty about the type of the timeout argument.

This internally involved a good bit of refactoring to share as much code as
possible between TCP servers and pipe servers, but the core implementation did
not change drastically as part of this commit.

cc #13523
Add a regex crate to the Rust distribution.

Also adds a regex_macros crate, which provides natively compiled
regular expressions with a syntax extension.

Closes #3591.

RFC: 0007-regexps
mk: Copy fewer libraries into the host artifacts
Cleaned up os::consts. The module only exposes constants for the target OS and arch.

Constants for other OS's and arch's must be defined manually.
[breaking-change]
auto merge of #13697 : pongad/rust/consts, r=alexcrichton

I decided to put architecture constants in another mod. They are not used, so a part of me is thinking of just getting rid of them altogether. The rest should be similar to what @brson wants.
Fixes #13536