Description:
------------
parse_url will fail for urls that don't have a scheme, but do have a port

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

print_r(parse_url('//example.org:81/hi?a=b#c=d'));
print_r(parse_url('//example.org/hi?a=b#c=d'));

Expected result:
----------------
Array
(
    [host] => example.org
    [port] => 81
    [path] => /hi
    [query] => a=b
    [fragment] => c=d
)
Array
(
    [host] => example.org
    [path] => /hi
    [query] => a=b
    [fragment] => c=d
)

Actual result:
--------------
Array
(
    [host] => example.org
    [path] => /hi
    [query] => a=b
    [fragment] => c=d
)