The standard library's first real content beyond printers. Everything is
in-place over a slice, because there is no allocator and nowhere to put a copy
- and a slice aliases its owner's storage, so sorting one sorts the original.
No generics means no single sort. Each is spelled per concrete type, which is a
cost paid deliberately rather than worked around.
parse-i64 is written in Flan rather than bound to strtoll, which answers 0 for
an empty string, for a string of letters, and for a genuine zero, and reports
overflow through errno.