Now that zig1.wasm is updated, apply the matching standard library
changes.
The main one is in `std.builtin.Type`, where `alignment` fields now have
type `?usize` rather than `comptime_int`.
Additionally, we need to add explicit backing integers to some packed
unions, because (due to https://github.com/ziglang/zig/issues/24714)
they need explicit backing integers to be used in `extern` contexts.
This change could not happen before now, because prior to this branch,
packed unions did not allow explicit backing integer types (that is,
this branch implemented https://github.com/ziglang/zig/issues/25350).
It is now composed of these main sections:
* Declarations that are shared among all operating systems.
* Declarations that have the same name, but different type signatures
depending on the operating system. Often multiple operating systems
share the same type signatures however.
* Declarations that are specific to a single operating system.
- These are imported one per line so you can see where they come from,
protected by a comptime block to prevent accessing the wrong one.
Closes#19352 by changing the convention to making types `void` and
functions `{}`, so that it becomes possible to update `@hasDecl` sites
to use `@TypeOf(f) != void` or `T != void`. Happily, this ended up
removing some duplicate logic and update some bitrotted feature
detection checks.
A handful of types have been modified to gain namespacing and type
safety. This is a breaking change.
Oh, and the last usage of `usingnamespace` site is eliminated.
dwarf: fixup x86 register mapping logic
dwarf: change the register context update to update in-place instead of copying
debug: always print the unwind error type
Move to c/darwin.zig as they really are libSystem/libc imports/wrappers.
As an added bonus, get rid of the nasty `usingnamespace`s which are now
unneeded.
Finally, add `os.ptrace` but currently only implemented on darwin.
Matthew Lugg