Description:
------------
parse_str returns a wrong result if param start with dot (.)

parse_str('.a=1&.b=2', $arr); 

This issue happend in whole versions of php.

Test script:
---------------
parse_str('.a=1&.b=2', $array);

Expected result:
----------------
Array
(
    [.a] => 1
    [.b] => 2
)


Actual result:
--------------
Array
(
    [_a] => 1
    [_b] => 2
)