Description:
------------
When using \p{L} on accented letters, the resulting match is truncated and therefore invalid UTF-8.

Examples:

à = C3A0 is returned as C3
é = C3A9 is returned as C3


Test script:
---------------
$str = 'Voilà déjà';

display($str);

preg_match_all('/\p{L}+/', $str, $matches);

foreach ($matches[0] as $match) {
    display($match);
}

function display($str) {
    echo bin2hex($str), ' ';
    var_export(mb_check_encoding($str, 'UTF-8'));
    echo PHP_EOL;
}

Expected result:
----------------
566f696cc3a02064c3a96ac3a0 true
566f696cc3a0 true
64c3a9 true
6ac3a0 true


Actual result:
--------------
566f696cc3a02064c3a96ac3a0 true
566f696cc3 false
64c3 false
6ac3 false