[Xymon] 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In https://bugs.debian.org/999921 Yavor Doganov provided a patch to convert xymon from outdated pcre3 to pcre2.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