More security hacking.
* Add TBvalid_uid() function to regex uid's. To be used throughout the system. Eventually add routines for checking other things like pids and eids, etc. * Regex the uid value we get from the cookie, and switch to $_COOKIE superglobal. * Strict regex checking in DOLOGIN() of uid. * Change login.php to use superglobals, and general tightening of parameter checking.