Merge upstream

Previously, i8 and i16 was careless w.r.t. the top bits,
because they were only used by v128, which uses Bytes.get/set that
appropriate masks the top bits when storing into the byte array.

With this change, i8 and i16 are self contained small integers
implemented using int32. They are always stored signed-extended, e.g.
INT8_MIN (-128) is stored as 0xffffff80.

This requires adding sign-extension operation (Rep.sx) in a couple of
places, that will make sure to extend the sign bit to the rest of the
int32.

Also add a small, non-exhaustive test for these small integers in a new
file tests/smallint.ml. This is the first ml test we are adding (all
previous tests are wasm/wast tests that we run using the interpreter),
so there are some modifications to the Makefile to build and run this
test (make smallinttest, make test will also run it).

This test is in the tests/ folder to avoid a conflict with a Makefile goal
test/x to run x.wast in ../test/core, otherwise it tries to run smallint.ml as
a wast test.
Co-authored-by: NAndreas Rossberg <rossberg@mpi-sws.org>

Based on comments from https://github.com/WebAssembly/spec/pull/1391.

Merge upstream

'%F' is not a supported format, see
https://github.com/sphinx-doc/sphinx/blob/4.x/sphinx/util/i18n.py#L133,
it is also not supported in Python's strftime/strptime
https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior.

It is however supported in strftime
(https://man7.org/linux/man-pages/man3/strftime.3.html) and defined to
be "%Y-%m-%d", which is supported by sphinx.

This allows us to drop some manual links removal in mathjax2katex.py.

Changes:
https://www.sphinx-doc.org/en/master/changes.html#release-4-0-0-released-may-09-2021

Things to note:

- docutils updated to 0.17
https://docutils.sourceforge.io/RELEASE-NOTES.html#release-0-17-2021-04-03
the big change here is to use semantic elements, <div class="section">
is now <section>, I see this a whole bunch when I diff the output HTML.
- supposedly some html themes break due to the docutils change, probably
due to divs not matching, I don't see any visible breakage, so it should
be fine
- mathjax 3
https://docs.mathjax.org/en/latest/upgrading/whats-new-3.0.html it's
faster to render, we need to tweak our configuration a bit, to
camelCase, so updated it in conf.py

I diffed the output html, some differences I noted:

- div -> section as noted above
- a new meta tag for Docutils
- link tag for css, the type and href attributs swapped places
- script tag for documetation_options, id and data-url_root swapped
places
- some css changes in sphinx css files
Co-authored-by: NMs2ger <Ms2ger@gmail.com>

Follow-up to #1384 to add checks for all numeric type.

Fixes #1250.

v0.11.0 added trust setting that indicates if input text is trusted,
this breaks \href.
Update to v0.13.19 which accepts a command line flag --trust to trust
all inputs.

I diffed the singlehtml output, it looks like the only changes are in
certain text that were:

<span class="mord mathsf">i</span><span class="mord
mathsf">3</span><span class="mord mathsf">2</span>

became

<span class="mord mathsf">i32</span>

which is a nice simplification.

For #1250. More tests for different data types in a follow-up.

This syncs the changes made in conf.py to bikeshed/conf.py.

Our current version of sphinx doesn't limit the supported docutils
versions, and 0.18.0 breaks something
(https://docutils.sourceforge.io/RELEASE-NOTES.html#release-0-18-2021-10-26
likely the new meta node)

3.5.4 restricts the docutils versions:
https://www.sphinx-doc.org/en/master/changes.html#release-3-5-4-released-apr-11-2021

Merge upstream

Similar to 5893af5b but for integers,
this is also a type mismatch, but should first be caught at parse time.

Several WebAssembly organization repositories have changed their default
branch from "master" to "main": see WebAssembly/design#1417 for details.
This PR updates URLs in the spec repository to point to "main" instead of
"master", for repositories which have done so.

Default branch is now main, so all the PRs are based on main, which
means the actions aren't currently triggered, since they only run on
push to master. Update it to main.

Since we have the main->master mirror, we should still be testing, but
it is a bit delayed (only after the mirror I think, and not on the PR).

* Add Changelog

* Comments

* Split narrow

* Regroup instructions

Name memarg arguments

Sync upstream

Fixes #509.

[spec] Refactor spec to align with interpreter

[spec] Rename simd->vec types