We already have a LICENSE file that covers the Zig Standard Library. We
no longer need to remind everyone that the license is MIT in every single
file.
Previously this was introduced to clarify the situation for a fork of
Zig that made Zig's LICENSE file harder to find, and replaced it with
their own license that required annual payments to their company.
However that fork now appears to be dead. So there is no need to
reinforce the copyright notice in every single file.
The primary purpose of this change is to eliminate one usage of
`usingnamespace` in the standard library - specifically the usage for
errno values in `std.os.linux`.
This is accomplished by truncating the `E` prefix from error values, and
making errno a proper enum.
A similar strategy can be used to eliminate some other `usingnamespace`
sites in the std lib.
This commit updates the WASI imports to use `wasi_snapshot_preview1`
instead of the old `wasi_unstable`. There are some minor ABI
differences between the two, however, the main motivator for using
the latest "stable" snapshot (aka preview1) is that, at least in
Wasmtime, there has been a lot of improvement work put into preview1
and unfortunately I might add, the improvements were not (in full)
backported to `wasi_unstable` snapshot.
Also, this commit removes the optional bound on the pointer to
`environ_get` syscall.
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.
