See <https://bugs.ruby-lang.org/issues/19417#note-3>.

https://unicode.org/reports/tr18/#word states word should match join_control chars.

It did not previously:

```ruby
[*0x0..0xD799, *0xE000..0x10FFFF].map { |n| n.chr 'utf-8' } => all_chars
all_chars.grep(/\p{join_control}/) => jc
jc.count # => 2
jc.grep(/\p{word}/).count # => 0
```
[Backport #19417]

---

Backporting note: I regenerated `enc/unicode/15.0.0/name2ctype.h` using
`make update-unicode`.

Ruby uses a recursive algorithm for handling control/meta escapes
in strings (read_escape).  However, the equivalent code for regexps
(tokadd_escape) in did not use a recursive algorithm.  Due to this,
Handling of control/meta escapes in regexp did not have the same
behavior as in strings, leading to behavior such as the following
returning nil:

```ruby
/\c\xFF/ =~ "\c\xFF"
```

Switch the code for handling \c, \C and \M in literal regexps to
use the same code as for strings (read_escape), to keep behavior
consistent between the two.

Fixes [Bug #14367]