Revert "Revert Ruby 1.9 dependency, it should stay on default. I've misread"
Accidentally I got the wrong text wrong and thus did something good,
so return to it; e.g., Ruby 1.9 by default.

This reverts commit b185d989a82a1e03a2cba824cb554b0ea8aa8e1e.
Cleanup google-gadgets:
  * Remove outdated TODO;
  * Add proper REGRESS_IS_INTERACTIVE;
  * Cleanup dependencies and add XDG goo;
  * Add some comments to patches.
Clarify that we're not interested in l10n of non-stable KDE4 versions.
Many cleanups for Virtuoso:
  * Bring back external libwbxml2 support;
  * Force disabling of Kerberos: Virtuoso supports MIT one only,
    and it's too much patching;
  * Fix some warnings looking too dangerous (will be sent upstream);
  * Add some comments to patches.