Reimplement access to log table in functions notify_login_failures() and count_login_failures()

Enable standard logstore plugin for both tests below.

Test 1

1. set config 'notifyloginthreshold' to 1
2. set config 'notifyloginfailures' to a user which can receive emails
3. Login to site incorrectly 2 times using :-
   1. a valid username
   2. an invalid username
   3. a invalid username from a different ip, beside your own
4. Login correctly to the site twice.
5. Run cron, make sure an email is sent to the user selected in notifyloginthreshold, with a report that gives details about each incorrect login information with time, ip and username.
6. Make sure the link to log reports in the email works.

Test 2

1. Before applying the patch, set displayloginfailures config to something beside "nobody".
2. Apply the patch, and upgrade.
3. Make sure now displayloginfailures is a checkbox and not a select and is checked.
4. Do incorrect logins with valid username.
5. Login as that user, and make sure you get a message, just below the logging box saying "x failed logins since your last login"

Test 3
Run unit tests under user/tests/userlib_test.php