Patch: PCRE2 support

Hi!

In https://bugs.debian.org/999921 Yavor Doganov provided a patch to
convert xymon from outdated pcre3 to pcre2.
Since I didn't see this patch here on the list, I'll forward it here.

Currently it's against 4.3.30, but Yavor offered to rebase it on
4.4-alpha.

It would be great if you could get rid of pcre3.

Greetings
Roland