(breaking) std.Buffer => std.ArrayListSentineled(u8, 0)

This new name (and the fact that it is a function returning a type) will
make it more clear which use cases are better suited for ArrayList and
which are better suited for ArrayListSentineled.

Also for consistency with ArrayList,
 * `append` => `appendSlice`
 * `appendByte` => `append`

Thanks daurnimator for pointing out the confusion of std.Buffer.
2e806682f4Andrew Kelley committed on 4/1/2020, 5:30:07 PMparent553f0e0
18 files changedLine totals unavailable