Add CAPTCHA validation
On validation connection error, always show a message and add the
CAPTCHA anyway.
Removed extra logging statements.

Were mostly left-over debugging stuff.

The one for an uninterpretable response was left but properly changed to
be a call to $.log
Style: use ' over "

Also use $.id where possible.
Alignment style.

Also remove a few unneeded conditionals. Seems having the entries passed
to GM_xmlhttpRequest as undefined is fine.
Tweak response reading logic.

$.id seems to take one argument. It still works the old way for some
reason, but is probably relying on some strange behavior we shouldn't
take for granted.
Don't duplicate "manual_challenge" response for checked captchas.
Merge pull request #183 from Macil/captchacheck

CAPTCHA checking before posting