Description:
------------
Locale::parseLocale (and locale_parse) is not able to parse locale with advanced agruments since PHP 5.6.28, 7.0.14 and 7.1.x (see https://3v4l.org/rRZK6)

Test script:
---------------
<?php

var_dump(Locale::parseLocale('cs_cz'));

var_dump(Locale::parseLocale('cs_Latn_CZ_VAR1_VAR2_X_PRI1_PRI2@calendar=iso8601;colbackwards=yes;colcasefirst=lower;collation=phonebook;currency=CZK;numbers=arab'));

Expected result:
----------------
array(2) {
  ["language"]=> string(2) "cs"
  ["region"]=> string(2) "CZ"
}
array(7) {
  ["language"]=> string(2) "cs"
  ["script"]=> string(4) "Latn"
  ["region"]=> string(2) "CZ"
  ["variant0"]=> string(4) "VAR1"
  ["variant1"]=> string(4) "VAR2"
  ["private0"]=> string(4) "PRI1"
  ["private1"]=> string(103) "PRI2@calendar=iso8601;colbackwards=yes;colcasefirst=lower;collation=phonebook;currency=CZK;numbers=arab"
}

Actual result:
--------------
array(2) {
  ["language"]=> string(2) "cs"
  ["region"]=> string(2) "CZ"
}
NULL