Description:
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Calling Locale::lookup() / locale_lookup() hangs if no match is found and the default locale should be returned. In PHP 7.0.9 it works as expected.

This error occurs no matter if the $canonicalize argument is true or false.

Test script:
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<?php
echo Locale::lookup(['en-Latn-US', 'sl', 'sl-IT'], 'en-US', true, 'de-DE');
//echo locale_lookup(['en-Latn-US', 'sl', 'sl-IT'], 'en-US', true, 'de-DE');

Expected result:
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de-DE

Actual result:
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[script timeout/server error]