* Delete `std.net.TmpWinAddr`. I don't think that was ever meant to
be a real thing.
* Delete `std.net.OsAddress`. This abstraction was not helpful.
* Rename `std.net.Address` to `std.net.IpAddress`. It is now an extern
union of IPv4 and IPv6 addresses.
* Move `std.net.parseIp4` and `std.net.parseIp6` to the
`std.net.IpAddress` namespace. They now return `IpAddress` instead of
`u32` and `std.net.Ip6Addr`, which is deleted.
* Add `std.net.IpAddress.parse` which accepts a port and parses either
an IPv4 or IPv6 address.
* Add `std.net.IpAddress.parseExpectingFamily` which additionally
accepts a `family` parameter.
* `std.net.IpAddress.initIp4` and `std.net.IpAddress.initIp6` are
improved to directly take the address fields instead of a weird
in-between type.
* `std.net.IpAddress.port` is renamed to `std.net.IpAddress.getPort`.
* Added `std.net.IpAddress.setPort`.
* `os.sockaddr` struct on all targets is improved to match the
corresponding system struct. Previously I had made it a union of
sockaddr_in, sockaddr_in6, and sockaddr_un. The new abstraction for
this is now `std.net.IpAddress`.
* `os.sockaddr` and related bits are added for Windows.
* `os.sockaddr` and related bits now have the `zero` fields default
to zero initialization, and `len` fields default to the correct size.
This is enough to abstract the differences across targets, and so
no more switch on the target OS is needed in `std.net.IpAddress`.
* Add the missing `os.sockaddr_un` on FreeBSD and NetBSD.
* `std.net.IpAddress.initPosix` now takes a pointer to `os.sockaddr`.
It had the downside of running all the comptime blocks and resolving
all the usingnamespaces of each system, when just trying to discover if
the current system is a particular one.
For Darwin, where it's nice to use `std.Target.current.isDarwin()`, this
demonstrates the utility that #425 would provide.
* All the data types from `@import("builtin")` are moved to
`@import("std").builtin`. The target-related types are moved
to `std.Target`. This allows the data types to have methods, such as
`std.Target.current.isDarwin()`.
* `std.os.windows.subsystem` is moved to
`std.Target.current.subsystem`.
* Remove the concept of the panic package from the compiler
implementation. Instead, `std.builtin.panic` is always the panic
function. It checks for `@hasDecl(@import("root"), "panic")`,
or else provides a default implementation.
This is an important step for multibuilds (#3028). Without this change,
the types inside the builtin namespace look like different types, when
trying to merge builds with different target settings. With this change,
Zig can figure out that, e.g., `std.builtin.Os` (the enum type) from one
compilation and `std.builtin.Os` from another compilation are the same
type, even if the target OS value differs.
