Upgrade to PCRE2

[markos]

For some reason issue 83 was removed, readding.

[tnias]

I just got notified that NixOS will get rid of pcre this release cycle (NixOS/nixpkgs#356387).

Other distros are also doing that.

• Debian removed it in Debian 13
• OpenSuse removed it in tumbleweed¹
• fedora deprecated it and it is no longer available in rawhide¹, so I assume they also removed it

There is no official guide to migrate from pcre to pcre2, but there are a lot of references in PCRE2Project/pcre2#51. Maybe they are helpful.

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¹ rawhide and tumbleweed are the codenames for their development versions, that will become the next release

[markos]

@tnias pcre migration will happen in 5.5 as it behaves differently than the previous version and will break compabitility.