* std.c: consolidate some definitions, making them share code. For
example, freebsd, dragonfly, and openbsd can all share the same
`pthread_mutex_t` definition.
* add type safety to std.c.O
- this caught a bug where mode flags were incorrectly passed as the
open flags.
* 3 fewer uses of usingnamespace keyword
* as per convention, remove purposeless field prefixes from struct field
names even if they have those prefixes in the corresponding C code.
* fix incorrect wasi libc Stat definition
* remove C definitions from incorrectly being in std.os.wasi
* make std.os.wasi definitions type safe
* go through wasi native APIs even when linking libc because the libc
APIs are problematic and wasteful
* don't expose WASI definitions in std.posix
* remove std.os.wasi.rights_t.ALL: this is a footgun. should it be all
future rights too? or only all current rights known? both are
the wrong answer.
* Replaces the exit assembly with the function from std.
* Reads the top-of-stack struct at program startup that can get information
like the pid.
* Changes the read and write functions to use the Pread and Pwrite syscalls
instead of the depreciated _READ and _WRITE
* Changes the openat function to use flags instead of perms.
Plan9 does not support perms when opening, just when creating.
* Adds an errstr function to read the errstr buf created by the kernel
Implements issue #6451.
This was needed to support allocation on Plan 9 and now other operating
systems like DOS can also use it.
It is a modified version of the WasmAllocator since wasm also uses a
sbrk-esque allocation system.
This commit also adds the necessary system bits for sbrk to work on plan 9.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
