Caught while tests were running for core.
Fatal error:
Call to undefined method CaptchaSessionStore::clearAll() in
ConfirmEdit/tests/CaptchaAuthenticationRequestTest.php
on line 13
Change-Id: I3a9f5b315eb114cb12ea4071f8da9079f797fcf6
Also update MathCaptcha so that it works with recent versions of
Math (and breaks with old ones). Also fix MathCaptcha API output,
which used to send the question in plaintext.
Bug: T110302
Change-Id: I0da671a546700110d789b79a3089460abd9cce3b
Depends-On: I8b52ec8ddf494f23941807638f149f15b5e46b0c
