Otherwise we will fail build with:

    PCRE2.xs:315:23: error: ‘PL_core_reg_engine’ undeclared (first use in this function)

Note PCRE2 likely will not build against most of 5.37 up until 5.37.8,
where the Perl_re_op_compile() function was marked in embed.fnc as
available to extensions (with the right define).

logical_parens needs to be set up the same as nparens unless
branch reset is in use (?|(...)|(...)) buffers are now separated
into logical buffers (eg $1) and physical buffers. In the case
of a branch reset like above there would be two physical buffers,
and 1 logical buffer.

I dont think PCRE2 does branch reset properly, so we can just
default it to the same value of nparens.

This patch also includes changes to set re->lastparen and
re->lastcloseparen in the exec sub, and not in the compile sub.
Last paren indicates the highest capture buffer that has content,
and lastcloseparen indicates the last capture buffer that match
so that we can support $^N. These two values are subtly different
and are not necessarily the same, although usually they are.

This is probably not the most efficient way to deal with this,
but we cant just pointer copy the buffer. It might be modified
or freed while the regex is still alive, and then bad things happen
when the regex is freed. Instead we just clone it with savepvn()

Ideally we would more closely mimic the behavior of core in this
regard, so that we can take advantage of perl level COW support
to get a cheaper string clone.