Merge JSON 2.7.2

  > https://github.com/flori/json/pull/525
  > Rename escape_slash in script_safe and also escape E+2028 and E+2029

  Co-authored-by: Jean Boussier <jean.boussier@gmail.com>

  > https://github.com/flori/json/pull/454
  > Remove unnecessary initialization of create_id in JSON.parse()

  Co-authored-by: Watson <watson1978@gmail.com>

It is rather common to directly interpolate JSON string inside
<script> tags in HTML as to provide configuration or parameters to a
script.

However this may lead to XSS vulnerabilities, to prevent that 3
characters need to be escaped:

  - `/` (forward slash)
  - `U+2028` (LINE SEPARATOR)
  - `U+2029` (PARAGRAPH SEPARATOR)

The forward slash need to be escaped to prevent closing the script
tag early, and the other two are valid JSON but invalid Javascript
and can be used to break JS parsing.

Given that the intent of escaping forward slash is the same than escaping
U+2028 and U+2029, I chos to rename and repurpose the existing `escape_slash`
option.

The C extension defines an `included` hook for the
`JSON::Ext::Generator::GeneratorMethods::String` module but neglects to
call `super` in the hook. This can break the functionality of various
other code that rely on the fact that `included` on `Module` will always
be called.

https://github.com/flori/json/commit/cd8bbe56a3

Split `PACKED_STRUCT` and `PACKED_STRUCT_UNALIGNED` macros into the
macros bellow:
* `RBIMPL_ATTR_PACKED_STRUCT_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_END`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END`

It makes testing for JSON errors very tedious. You either have
to use a Regexp or to regularly update all your assertions
when JSON is upgraded.

https://github.com/flori/json/commit/de9eb1d28e