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
rustc: Don't die on 0-length pattern idents

These often crop up when using default methods that don't actually bind their
argument names.

Closes #13775
Fix typo
Remove extra semicolons
Suggested revisions to PR 13676.

Most important: distinguish function decl sugar for omitting `-> ()`
from type inference on closures.  I also tried to add a couple more
examples to further emphasize this distinction.  Note that this sugar
(of omitting `-> ()`) is actually already briefly mentioned in an
earlier section, so it is a little tricky deciding whether to put more
material here, or to move it up to the previous section.

Other drive-by fixes:

 * Fix the line length of the code blocks to fit in the width provided
   in the rendered HTML

 * Some minor revisions to wording (e.g. try to clarify in some cases
   where a type mismatch is arising).
native: Always open a file with Open/Write modes

Previously, windows was using the CREATE_NEW flag which fails if the file
previously existed, which differed from the unix semantics. This alters the
opening to use the OPEN_ALWAYS flag to mirror the unix semantics.

Closes #13861
Merge pull request #1 from pnkfelix/clarify-omit-unit-vs-inference

Suggested revisions to PR 13676.
Add a `graphviz` crate for making .dot files to layout and render graphs.
Updated maybe_owned_vec with review feedback.

Namely:

 * Added conversion traits both to and from the various vector types,
   analogous to how `str::MaybeOwned` works with `str::IntoMaybeOwned`
   and `str::Str`.  This led me to add the `FixedLen` variant of
   `MaybeOwnedVector` for interoperability with `std::slice`.

 * Revised client example code to make use of `into_maybe_owned`

 * Added implementations of `Show` and `CloneableVector` for
   `MaybeOwnedVector`.

 * As suggested by kballard, added `into_vec` method that is analogous
   to `CloneableVector::into_owned` except it produces a `Vec` rather
   than a `~[T]`.
rustc: Add some suppot for mixing rlibs and dylibs

Currently, rustc requires that a linkage be a product of 100% rlibs or 100%
dylibs. This is to satisfy the requirement that each object appear at most once
in the final output products. This is a bit limiting, and the upcoming libcore
library cannot exist as a dylib, so these rules must change.

The goal of this commit is to enable *some* use cases for mixing rlibs and
dylibs, primarily libcore's use case. It is not targeted at allowing an
exhaustive number of linkage flavors.

There is a new dependency_format module in rustc which calculates what format
each upstream library should be linked as in each output type of the current
unit of compilation. The module itself contains many gory details about what's
going on here.

cc #10729
rustc: Remove the session building_library flag

This has long since not been too relevant since the introduction of many crate
type outputs. This commit removes the flag entirely, adjusting all logic to do
the most reasonable thing when building both a library and an executable.

Closes #13337
Generalize stats from f64 to the Float trait
Use is_zero
Remove comment about semicolons for inner attributes from docs and adjust comments.
Recommend autoload instead of require

Lazy loading with autoload will result in faster startup time for Emacs
users and is generally the recommended approach for major modes.
shootout-spectralnorm tweaks

- using libgreen to optimize CPU usage
- less tasks to limit wasted resources

Here, on a one core 2 threads CPU, new version is ~1.2 faster.  May
be better with more core.