Revert "Remove captcha doubling. Only change now made to v1 captcha is [blank captcha] -> "al pacino"."

This reverts commit f543232af98677910ce17ec0e690db1f9c0192a9.
Revert "On closer examination, the captcha is accepting more or less arbitrary input."

This reverts commit 1681beaab8c0af4504534011ef98401edaa16cec.
Revert "Merge branch 'old-captcha'; allow selection of old or new captcha."

This reverts commit c7433d9271717df3f0f8d64e22abf73e85f8a5ca, reversing
changes made to 68dbb73c4eceec13cdc56550f8181adc28ab65a2.