(https://github.com/ruby/fiddle/pull/155)

GitHub: fix https://github.com/ruby/fiddle/pull/153

mkmf requires fileutils. JRuby doesn't like it.

https://github.com/ruby/fiddle/commit/df4bd21fc3

(https://github.com/ruby/fiddle/pull/157)

The GCC warning puts undefined macro names in double quotes while clang
puts them in single quotes.

https://github.com/ruby/fiddle/commit/7dcb40bccb

Fix GH-145

Rename `lib/fiddle/jruby.rb` to `lib/fiddle/ffi_backend.rb` as a generic
ffi gem API based implementation.
JRuby and TruffleRuby use `lib/fiddle/ffi_backend.rb`.

---------

Co-authored-by: Benoit Daloze <eregontp@gmail.com>

(https://github.com/ruby/fiddle/pull/139)

https://github.com/ruby/fiddle/commit/91d0ea9849

Co-authored-by: Sutou Kouhei <kou@clear-code.com>

Fix GH-104

lib/fiddle/jruby.rb is based on

https://github.com/jruby/jruby/blob/master/lib/ruby/stdlib/fiddle/jruby.rb
.

Here are changes for it:

* Move `Fiddle::TYPE_*` to `Fiddle::Types::*`
* Add `Fiddle::Types::VARIADIC`
* Add `Fiddle::Types::CONST_STRING`
* Add `Fiddle::Types::BOOL`
* Add `Fiddle::Types::INT8_T`
* Add `Fiddle::Types::UINT8_T`
* Add `Fiddle::Types::INT16_T`
* Add `Fiddle::Types::UINT16_T`
* Add `Fiddle::Types::INT32_T`
* Add `Fiddle::Types::UINT32_T`
* Add `Fiddle::Types::INT64_T`
* Add `Fiddle::Types::UINT64_T`
* Add more `Fiddle::ALIGN_*` for the above new `Fiddle::Types::*`
* Add more `Fiddle::SIZEOF_*` for the above new `Fiddle::Types::*`
* Add support for specifying type as not only `Fiddle::Types::*` but
also `Symbol` like `:int`
* Add support for variable size arguments in `Fiddle::Function`
* Add `Fiddle::Closure#free`
* Add `Fiddle::Closure#freed?`
* Add `Fiddle::Error` as base the error class
* Add `Fiddle::Pointer#call_free` and stop using `FFI::AutoPointer` in
`Fiddle::Pointer`
* Add support for `Fiddle::Pointer.malloc {}` `Fiddle::Pointer`
* Add support for `Fiddle::Pointer#free=`
* Add `Fiddle::Pointer#freed?`
* Use binary string not C string for `Fiddle::Pointer#[]`
* Add `Fiddle::Handle.sym_defined?`
* Add `Fiddle::Handle#sym_defined?`
* Add `Fiddle::Handle::DEFAULT`
* Add `Fiddle::ClearedReferenceError`
* Add no-op `Fiddle::Pinned`

Some features are still "not implemented". So there are some "omit"s for
JRuby in tests.

(https://github.com/ruby/fiddle/pull/134)

```
In file included from ../../../../ext/fiddle/fiddle.h:46:
/opt/local/include/ffi.h:477:5: warning: 'FFI_GO_CLOSURES' is not defined, evaluates to 0 [-Wundef]
    ^
```

c.f. https://github.com/libffi/libffi/pull/796

https://github.com/ruby/fiddle/commit/d4feb57098

https://bugs.ruby-lang.org/issues/18571

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
Co-authored-by: Sutou Kouhei <kou@clear-code.com>

https://github.com/ruby/fiddle/commit/4ee1c6fc4b