Use always only lowercase version of username.

When using authentication module (ldap, smb, pop etc...) and postgres-database multiple moodle
users were created for usernames like 'Username' 'username' 'userName'

lib/moodlelib.php

@@ -483,7 +483,9 @@ function get_moodle_cookie() {
 function create_user_record($username, $password) {
 /// Creates a bare-bones user record 
     global $REMOTE_ADDR, $CFG;
-
+    
+    $username = strtolower($username);
+    
     if (function_exists(auth_get_userinfo)) {
         if ($newinfo = auth_get_userinfo($username)) {
             foreach ($newinfo as $key => $value){

login/index.php

@@ -21,7 +21,7 @@
 
 
     if ($frm = data_submitted()) {
-
+        $frm->username = strtolower($frm->username);
         $user = authenticate_user_login($frm->username, $frm->password);
 
         update_login_count();

login/signup.php

@@ -5,7 +5,7 @@
     require_once("../auth/$CFG->auth/lib.php");
 
 	if ($user = data_submitted()) {
-
+        $user->username= strtolower($user->username);
 		validate_form($user, $err);
 
 		if (count((array)$err) == 0) {
@@ -74,7 +74,7 @@
  *****************************************************************************/
 
 function validate_form($user, &$err) {
-  global $CFG;
+    global $CFG;
 	if (empty($user->username))
 		$err->username = get_string("missingusername");
 

user/edit.php

@@ -43,7 +43,7 @@
 /// If data submitted, then process and store.
 
 	if ($usernew = data_submitted()) {
-
+        $usernew->username = strtolower($usernew->username);
         $usernew->firstname = strip_tags($usernew->firstname);
         $usernew->lastname  = strip_tags($usernew->lastname);