MDL-44118 new environment check are all quiz attempts upgraded.

In Moodle 2.1, there was a major DB upgrade relating to questions, and
it was possible to delay some of that upgrade. Now, those DB tables are
changing again, and the time has come to insist that all the updata has
been upgraded (or deleted).

lib/customcheckslib.php

@@ -15,15 +15,16 @@
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
 /**
- * This is a one-line short description of the file
+ * This is a place to put custom environment checks, if there is not a better place.
  *
  * This library contains a collection of functions able to perform
  * some custom checks executed by environmental tests (automatically
  * executed on install & upgrade and under petition in the admin block).
  *
- * Any function in this library must return:
+ * Any function in this library gets a environment_results object passed in.
+ * It must return:
  * - null: if the test isn't relevant and must not be showed (ignored)
- * - environment_results object with the status set to:
+ * - the environment_results object that was passed in, with the status set to:
  *     - true: if passed
  *     - false: if failed
  *