I don't use tool/sync_default_gem.rb because the last sync was incomplete.

Co-authored-by: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>
Co-authored-by: sinisterchipmunk <sinisterchipmunk@gmail.com>
Co-authored-by: Sutou Kouhei <kou@clear-code.com>

It's fixed in upstream.
https://github.com/MSP-Greg/ruby-loco/issues/4

https://github.com/ruby/fiddle/commit/2ae0ff4934

https://github.com/ruby/fiddle/commit/bb227c206d

https://github.com/ruby/fiddle/commit/fee175a8ff

* Add a "pinning" reference

A `Fiddle::Pinned` objects will prevent the objects they point to from
moving.  This is useful in the case where you need to pass a reference
to a C extension that keeps the address in a global and needs the
address to be stable.

For example:

```ruby
class Foo
  A = "hi" # this is an embedded string

  some_c_function A # A might move!
end
```

If `A` moves, then the underlying string buffer may also move.
`Fiddle::Pinned` will prevent the object from moving:

```ruby
class Foo
  A = "hi" # this is an embedded string

  A_pinner = Fiddle::Pinned.new(A) # :nodoc:

  some_c_function A # A can't move because of `Fiddle::Pinned`
end
```

This is a similar strategy to what Graal uses:

  https://www.graalvm.org/sdk/javadoc/org/graalvm/nativeimage/PinnedObject.html#getObject--

* rename global to match exception name

* Introduce generic Fiddle::Error and rearrange error classes

Fiddle::Error is the generic exception base class for Fiddle exceptions.
This commit introduces the class and rearranges Fiddle exceptions to
inherit from it.

https://github.com/ruby/fiddle/commit/ac52d00223

https://github.com/ruby/fiddle/commit/f16e7ff6e0

It loads `ext/fiddle/lib/fiddle/version.rb`, which causes constant
redefinition warning:

http://rubyci.s3.amazonaws.com/ubuntu2004/ruby-master/log/20200523T153003Z.log.html.gz
```
[ 6317/20193] TestDefaultGems#test_validate_gemspec/home/chkbuild/chkbuild/tmp/build/20200523T153003Z/ruby/ext/fiddle/lib/fiddle/version.rb:2: warning: already initialized constant Fiddle::VERSION
/home/chkbuild/chkbuild/tmp/build/20200523T153003Z/ruby/.ext/common/fiddle/version.rb:2: warning: previous definition of VERSION was here
 = 0.16 s
```

This changeset read the version by manual parsing hack which is also
used in stringio and zlib.

https://github.com/ruby/fiddle/commit/b04cb92d7b

https://github.com/ruby/fiddle/commit/9dcf64c096