Description:
------------
When using multiline mode in a regular expression, \s incorrectly matches a new-line character.

Reproduce code:
---------------
$info = <<<INFO
	Sender:
	Pages: 1
INFO;

preg_match_all('/^\s*([^:]+?):\s*(.*)$/m', $info, $matches, PREG_PATTERN_ORDER);

// combine into an array of key=>value pairs
$info = array_combine(array_map('strtolower', $matches[1]), $matches[2]);

var_dump($info);

Expected result:
----------------
array(2) {
  ["sender"]=>
  string(0) ""
  ["pages"]=>
  string(1) "1"
}

Actual result:
--------------
array(1) {
  ["sender"]=>
  string(8) "Pages: 1"
}