SQLInjection fixed in loginValidation.php

[eliasbiagioni]

Wapiti3 report in login.php request.
SQL Injection in:

POST /login.php HTTP/1.1
    Host: localhost:82
    Referer: http://localhost:82/login.php
    Content-Type: application/x-www-form-urlencoded

    user_name=alice&pass=%C2%BF%27%22%28&signinBtn=Sign+in

We added the fix with MySqli prepared statements to avoid SQLInjection.