It's not (reasonably) possible to do so though, because it would break so, so much legacy code. The only thing you can do is to add new functionality (e.g. the difference between A and W APIs - A is ASCII, W is UTF-16) or to shoehorn crap onto existing interfaces (again, A APIs to which you pass UTF-8 and pray for the best), but you cannot delete any publicly exposed API or modify existing types.
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It's not (reasonably) possible to do so though, because it would break so, so much legacy code. The only thing you can do is to add new functionality (e.g. the difference between A and W APIs - A is ASCII, W is UTF-16) or to shoehorn crap onto existing interfaces (again, A APIs to which you pass UTF-8 and pray for the best), but you cannot delete any publicly exposed API or modify existing types.