Don't display messages to configure CAPTCHA when part of an install profile

I'm bundling the CAPTCHA module as part of an install profile. Unfortunately CAPTCHA includes a hard coded message in captcha_install() that says, "You can now configure the CAPTCHA module for your site", with a link to the CAPTCHA configuration. However at this time, the site configuration isn't even finished and the user is still in install.php. If they were to follow the link, they would leave the installer before it was completed.

So to fix this, I'd like to propose that we only show the welcome messages if the module was installed through the normal interface. An easy way to check this is to simply see if MAINTENANCE_MODE is set to "install".

At the end of captcha_install() (but before the messages are set), add:

// Do not display messages if being installed as part of a profile.
if (defined('MAINTENANCE_MODE') && MAINTENANCE_MODE === 'install')) {
  return;
}