std.ArrayList support for [Read/Write]Buffers

[arxdeus]

[robbielyman]

sorry for the necro-bump, but i'd be curious about what isn't working with status quo libxev. for example to read into an ArrayList with libxev, just pass something like .{ .slice = list.unusedCapacitySlice() } to the call to read. to reuse the ArrayList when reading, make it a field of your userdata and update the list in the callback.