Description:
------------
new mysqli no longer accepts `ip:port` as first parameter (host)

`ip:port` works in PHP 7.1.3 and 7.0.17
`ip:port` does not work in PHP 7.1.4 and 7.0.18

```
# php --version
PHP 7.1.4 (cli) (built: Apr 25 2017 03:19:44) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
```
```
# php --version
PHP 7.0.18 (cli) (built: Apr 25 2017 03:43:44) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
```

Used php official container from https://hub.docker.com/_/php/
Enabled mysqli module with `docker-php-ext-install mysqli`


Test script:
---------------
<?php
$servername = "ensembldb.ensembl.org:3306";
$username = "anonymous";
$password = "";
$conn = new mysqli($servername, $username, $password);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 
echo "Connected successfully";
?>

Expected result:
----------------
Connected successfully

Actual result:
--------------
PHP Warning:  mysqli::__construct(): (HY000/2002): Failed to parse address "ensembldb.ensembl.org:3306:3306" in /root/pepe.php on line 7
Connection failed: Failed to parse address "ensembldb.ensembl.org:3306:3306"