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
Before, QuestyCaptcha answers were case-insensitive when there was
only one answer for a question, but they had to be lowercase when
there was an array of answers. This makes it so that when an array
of answers is provided for a question in $wgCaptchaQuestions, those
answers are case-insensitive.
Bug: T65272
Change-Id: I146b53cacf901c45ce27bd87fdf8125bfd2bc270