Description:
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IDN domains can contain hyphens in its name.

When we convert these domain names to punycode we end up with several hyphens in 
a row.
For example: xn----7sbbtkohtqhvkc8j.xn--p1ai (культура-пенза.рф)
Yet it is a valid domain name.

The regexp in the ext/filter/logical_filters.c:525 doens't allow multiple 
hyphens but two:

> ... (?:(?:(?:xn--)?[a-z0-9]+( ....

So if I try filter_var("asd@xn----7sbbtkohtqhvkc8j.xn--p1ai", 
FILTER_VALIDATE_EMAIL) it returns false.

I think valid regexp will be like (?:xn-(-)+)?[a-z0-9]+ yet I can't be sure 
since this regexp is 
really scary.

Test script:
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<?php

var_dump(filter_var("asd@xn----7sbbtkohtqhvkc8j.xn--p1ai", FILTER_VALIDATE_EMAIL));

Expected result:
----------------
string(35) "asd@xn----7sbbtkohtqhvkc8j.xn--p1ai"

Actual result:
--------------
bool(false)