Squashed 'vendor/tcloo-ext/' content from commit cd7d9a6

git-subtree-dir: vendor/tcloo-ext
git-subtree-split: cd7d9a6d8de91428deb096be3916d2ce6bd0221e
Merge commit '6e76cbb3a704cc96813b070d3bcf93140dc4ae61' as 'vendor/tcloo-ext'
Make use of TclOO::ext.