Another major change:
* Now login attempt counts are stored in the database, to prevent malicious
  users from deleting session cookies and being able to keep brute-forcing
  their way into an account. After 5 logins the login script requires a
  Captcha to be solved, until a user enters everything right (both login
  data and Captcha).
* Because the Captcha is now used on multiple pages, I put it in
  session_dbconnect.php, which is now renamed to multfunlib.php (contains
  multiple functions that are repeatedly used across the scripts).