[Issue 13717] `split` no longer defined by std.string

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13717

--- Comment #9 from hsteoh at quickfur.ath.cx ---
Actually, on second thoughts, does it make sense to deprecate them instead?
Based on the comment, seems they're supposed to be deprecated because they got
moved to other modules (std.array, std.algorithm, etc.).

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