Call idn_to_ascii with INTL_IDNA_VARIANT_UTS46
Call idn_to_ascii with INTL_IDNA_VARIANT_UTS46

Under PHP 7.2, calling `idn_to_ascii($idn)` results in a deprecation warning: 'INTL_IDNA_VARIANT_2003 is deprecated'
See https://secure.php.net/manual/en/function.idn-to-ascii.php 

Therefore, if possible, `idn_to_ascii($idn, 0, INTL_IDNA_VARIANT_UTS46)` should be used instead. `INTL_IDNA_VARIANT_UTS46` was introduced in PHP 5.4, so on versions before that, `idn_to_ascii($idn)` must still be used.

Fixed #1699
Alkarex/FreshRSS,aledeg/FreshRSS,romibi/FreshRSS,FreshRSS/FreshRSS,Alkarex/FreshRSS,marienfressinaud/FreshRSS,marienfressinaud/FreshRSS,marienfressinaud/FreshRSS,Alkarex/FreshRSS,aledeg/FreshRSS,aledeg/FreshRSS,romibi/FreshRSS,romibi/FreshRSS,FreshRSS/FreshRSS,FreshRSS/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,marienfressinaud/FreshRSS,romibi/FreshRSS,aledeg/FreshRSS