Make CAPTCHA implementations pluggable
Rename recaptcha to captcha_recaptcha
DMD 2.067 compatibility
Use ae.net.shutdown

ae.sys.shutdown is no longer usable for network programs as of
ae 8903671b5e71dcd65934e5492a8282d05aff605e
spam: Add subject keyword check
Add and switch to DCaptcha
posting: Clarify source of CAPTCHA errors
Tweak punctuation in CAPTCHA errors