Add option to block all IDN domains

[DL6ER]

@slawa

so I want a modified wildcard blocking that only looks at the first 4 characters of a domain and blocks it if it is xn--

I found the time to eventually implement GNU Extended Regular Expressions, see the announcement here:

Blocking via regex now available in FTLDNS

Originally published at: https://pi-hole.net/2018/04/24/blocking-via-regex-now-available-in-ftldns/ We have implemented GNU Extended Regular Expressions for blocking domains into FTLDNS (as used by popular tools such as egrep (or grep -E ...), awk, and emacs). To try it, you need to be participating in the FTLDNS beta test (see here for more details). This is a new feature and we invite you to test it out but you should expect some rough edges. We would also appreciate if you could help …

@slawa A suitable regex for you should be

BLOCKINGREGEX=xn--