captcha 6.x-2.0-rc2

A 6.x-2.0 release is coming closer!
The large architectural changes are (finally) over.
Only some small issues and kinks to work out.

Changes since DRUPAL-6--2-0-RC1:

• prerender handling of the 'captcha_response' form item is now only done if it is a textfield and not on e.g. the reCAPTCHA form construction, where it does not make sense.
• #473002: CAPTCHA API now provides a way to define a custom CAPTCHA validation function
• 6.x-2.0-beta5 made the case insensitive validation a global option (as a checkbox), but this is now changed to a "default CAPTCHA validation" option (as radio list), which describes better what it actually is (a default that can be overriden/ignored)
• #476288: showing CAPTCHA description is now controlled by explicit checkbox on admin interface instead of obscure "if not empty".
• Added a drop of jQuery for added usability for the CAPTCHA description
• Worked on CAPTCHA description usage/translation/workflow: CAPTCHA descriptions can now be reset with empty entry, tweaked UI strings, fixed bug in localized default CAPTCHA description.
• made image CAPTCHA settings more finegrained/explicit
• added jQuery niceness for image CAPTCHA settings page (distortion and noise level stuff)
• Various small fixes and tweaks.
• Various translation updates (pot file, Lithuanian, Dutch)