MDL-20245 grade: increased the length of the user_preferences::value column and added an exception to set_user_preference() is this new length is exceeded

Conflicts:

	lib/db/upgrade.php
	version.php

lib/moodlelib.php

@@ -1652,6 +1652,9 @@ function set_user_preference($name, $value, $user = null) {
         throw new coding_exception('Invalid value in set_user_preference() call, arrays are not allowed');
     }
     $value = (string)$value;
+    if (textlib::strlen($value) > 1333) { //value column maximum length is 1333 characters
+        throw new coding_exception('Invalid value in set_user_preference() call, value is is too long for the value column');
+    }
 
     if (is_null($user)) {
         $user = $USER;