* [blend2d] Update to 2021-03-17

* [blend2d] update port_versions

* [blend2d] Update to beta_2021-01-02

* [blend2d] update port_versions

* [vcpkg docs] add docs for manifest files

These are just for the maintainer docs,
not user docs.

* [vcpkg] EBNF-ify platform expression parsing

this modifies nothing about what strings are accepted or rejected,
it just moves stuff around.

also adds tests.

* [vcpkg docs] add manifest mode example

* [wip] docs for augustin

also fix tabs

* [vcpkg manifest] switch to using maps for features

* Apply suggestions from code review

* un-experimentize format-manifest

* flesh out the user manifest mode docs

* CRs

* billy CRs

* final personal pass-thru

* [vcpkg format-manifest] initial convert-control attempt

TODO: manifest comments! we should keep $directives

* Finalize x-format-manifest

First, fix Json::parse -- "\c", for any c, was incorrectly parsed.
It would emit the escaped character, and then parse the character, so
that `\b` would give you { '\b', 'b' }.

Second, canonicalize source paragraphs as we're parsing them. This found
an error in qt5 -- The `declarative` feature was listed twice, and we
now catch it, so I removed the second paragraph.

Add PlatformExpression::complexity to allow ordering platform
expressions in a somewhat reasonable way.

Notes:
  - We allow `all_modules` as a feature name for back-compat with
    paraview
  - In order to actually convert CONTROL to vcpkg.json, we'd need to
    rename the qt5 `default` feature.
  - We need to add support for $directives in x-format-manifest

* fix qt5 port

* format

* fix compile

* fix tests for canonicalization

* Clean up code

* add error message for nothing to format

* add extra_info field

* add `const X&` overloads for `Object::insert[_or_replace]`

* fix compile

* simple CRs

* add tests

* format

* Fix mosquitto port file

also unmerge a line

* fail the tests on malformed manifest

* fix format_all

* fix coroutine port-version

* format manifests