GitHub: fix https://github.com/ruby/fiddle/pull/107

Reported by nicholas a. evans. Thanks!!!

https://github.com/ruby/fiddle/commit/49ea1490df

GitHub: fix GH-102

It's for freeing a closure explicitly.

We can't use Fiddle::Closure before we fork the process. If we do it,
the process may be crashed with SELinux.

See https://github.com/ruby/fiddle/issues/102#issuecomment-1241763091
for details.

Reported by Vít Ondruch. Thanks!!!

https://github.com/ruby/fiddle/commit/a0ccc6bb1b

This helps to reduce repetition in code. Instead of doing "TYPE_*"
everywhere, you can do `include Fiddle::Types`, and write the type name
directly.

This PR is to help reduce repetition when writing Fiddle code. Right now
we have to type `TYPE_` everywhere, and you also have to include all of
`Fiddle` to access `TYPE_*` constants. With this change, you can just
include `Fiddle::Types` and it will shorten your code and also you only
have to include those constants.

Here is an example before:

```ruby
require "fiddle"

module MMAP
  # All Fiddle constants included
  include Fiddle

  def self.make_function name, args, ret
    ptr = Handle::DEFAULT[name]
    func = Function.new ptr, args, ret, name: name
    define_singleton_method name, &func.to_proc
  end

  make_function "munmap", [TYPE_VOIDP, # addr
                           TYPE_SIZE_T], # len
                           TYPE_INT

  make_function "mmap", [TYPE_VOIDP,
                         TYPE_SIZE_T,
                         TYPE_INT,
                         TYPE_INT,
                         TYPE_INT,
                         TYPE_INT], TYPE_VOIDP

  make_function "mprotect", [TYPE_VOIDP, TYPE_SIZE_T, TYPE_INT], TYPE_INT
end
```

After:

```ruby
require "fiddle"

module MMAP
  # Only type names included
  include Fiddle::Types

  def self.make_function name, args, ret
    ptr = Fiddle::Handle::DEFAULT[name]
    func = Fiddle::Function.new ptr, args, ret, name: name
    define_singleton_method name, &func.to_proc
  end

  make_function "munmap", [VOIDP, # addr
                           SIZE_T], # len
                           INT

  make_function "mmap", [VOIDP, SIZE_T, INT, INT, INT, INT], VOIDP

  make_function "mprotect", [VOIDP, SIZE_T, INT], INT
end
```

We only need to import the type names, and you don't have to type
`TYPE_` over and over. I think this makes Fiddle code easier to read.

https://github.com/ruby/fiddle/commit/49fa7233e5

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

This commit adds constants for unsigned values. Currently we can use `-`
to mean "unsigned", but I think having a specific name makes Fiddle more
user friendly. This commit continues to support `-`, but introduces
negative constants with "unsigned" names

I think this will help to eliminate [this
code](https://github.com/ruby/ruby/blob/3a56bf0bcc66e14ffe5ec89efc32ecfceed180f4/lib/mjit/c_type.rb#L31-L38)

https://github.com/ruby/fiddle/commit/2bef0f1082

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

https://github.com/ruby/fiddle/commit/4a71246645ccff001292c9d80b855b2ef5bf06c1

I need to get the offset of members inside sub structures.  This patch
adds sub-structure offset support for structs.

https://github.com/ruby/fiddle/commit/cf78eddbb6

* Add "offsetof" to Struct classes

I need to get the offset of a member inside a struct without allocating
the struct.  This patch adds an "offsetof" class method to structs that
are generated.

The usage is like this:

```ruby
MyStruct = struct [
  "int64_t i",
  "char c",
]

MyStruct.offsetof("i") # => 0
MyStruct.offsetof("c") # => 8
```

* Update test/fiddle/test_c_struct_builder.rb

Co-authored-by: Sutou Kouhei <kou@cozmixng.org>

https://github.com/ruby/fiddle/commit/4e3b60c5b6

Co-authored-by: Sutou Kouhei <kou@cozmixng.org>

https://github.com/ruby/fiddle/commit/049138b4b8

https://github.com/ruby/fiddle/commit/3784cfeec4