* delete the std/event/net directory
 * `std.event.Loop.waitUntilFdReadable` and related functions
   no longer have possibility of failure. On Linux, they fall
   back to poll() and then fall back to sleep().
 * add some missing `noasync` decorations in `std.event.Loop`
 * redo the `std.net.Server` API. it's quite nice now, but
   shutdown does not work cleanly. There is a race condition with
   close() that I am actively working on.
 * move `std.io.OutStream` to its own file to match `std.io.InStream`.
   I started working on making `write` integrated with evented I/O,
   but it got tricky so I backed off and filed #3557. However
   I did integrate `std.os.writev` and `std.os.pwritev` with evented I/O.
 * add `std.Target.stack_align`
 * move networking tests to `lib/std/net/test.zig`
 * add `std.net.tcpConnectToHost` and `std.net.tcpConnectToAddress`.
 * rename `error.UnknownName` to `error.UnknownHostName` within the
   context of DNS resolution.
 * add `std.os.readv`, which is integrated with evented I/O.
 * `std.os.preadv`, is now integrated with evented I/O.
 * `std.os.accept4` now asserts that ENOTSOCK and EOPNOTSUPP never
    occur (misuse of API), instead of returning errors.
 * `std.os.connect` is now integrated with evented I/O.
   `std.os.connect_async` is gone. Just use `std.os.connect`.
 * fix false positive dependency loop regarding async function frames
 * add more compile notes to help when dependency loops occur
   in determining whether a function is async.
 * ir: change an assert to ir_assert to make it easier to find
   workarounds for when such an assert is triggered. In this case
   it was trying to parse an IPv4 address at comptime.