std.c reorganization

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.

1 files changed, 0 insertions, 180 deletions

diff --git a/lib/std/c/emscripten.zig b/lib/std/c/emscripten.zig
deleted file mode 100644
index 0893289b14..0000000000
--- a/lib/std/c/emscripten.zig
+++ /dev/null
@@ -1,180 +0,0 @@
-const std = @import("../std.zig");
-const maxInt = std.math.maxInt;
-const emscripten = std.os.emscripten;
-
-pub const AF = emscripten.AF;
-pub const CLOCK = emscripten.CLOCK;
-pub const CPU_COUNT = emscripten.CPU_COUNT;
-pub const E = emscripten.E;
-pub const F = emscripten.F;
-pub const FD_CLOEXEC = emscripten.FD_CLOEXEC;
-pub const F_OK = emscripten.F_OK;
-pub const Flock = emscripten.Flock;
-pub const IFNAMESIZE = emscripten.IFNAMESIZE;
-pub const IOV_MAX = emscripten.IOV_MAX;
-pub const IPPROTO = emscripten.IPPROTO;
-pub const LOCK = emscripten.LOCK;
-pub const MADV = emscripten.MADV;
-pub const MSF = emscripten.MSF;
-pub const MSG = emscripten.MSG;
-pub const NAME_MAX = emscripten.NAME_MAX;
-pub const PATH_MAX = emscripten.PATH_MAX;
-pub const POLL = emscripten.POLL;
-pub const PROT = emscripten.PROT;
-pub const REG = emscripten.REG;
-pub const RLIM = emscripten.RLIM;
-pub const R_OK = emscripten.R_OK;
-pub const S = emscripten.S;
-pub const SA = emscripten.SA;
-pub const SEEK = emscripten.SEEK;
-pub const SHUT = emscripten.SHUT;
-pub const SIG = emscripten.SIG;
-pub const SIOCGIFINDEX = emscripten.SIOCGIFINDEX;
-pub const SO = emscripten.SO;
-pub const SOCK = emscripten.SOCK;
-pub const SOL = emscripten.SOL;
-pub const STDERR_FILENO = emscripten.STDERR_FILENO;
-pub const STDIN_FILENO = emscripten.STDIN_FILENO;
-pub const STDOUT_FILENO = emscripten.STDOUT_FILENO;
-pub const Sigaction = emscripten.Sigaction;
-pub const TCP = emscripten.TCP;
-pub const TCSA = emscripten.TCSA;
-pub const W = emscripten.W;
-pub const W_OK = emscripten.W_OK;
-pub const X_OK = emscripten.X_OK;
-pub const addrinfo = emscripten.addrinfo;
-pub const blkcnt_t = emscripten.blkcnt_t;
-pub const blksize_t = emscripten.blksize_t;
-pub const clock_t = emscripten.clock_t;
-pub const cpu_set_t = emscripten.cpu_set_t;
-pub const dev_t = emscripten.dev_t;
-pub const dl_phdr_info = emscripten.dl_phdr_info;
-pub const empty_sigset = emscripten.empty_sigset;
-pub const fd_t = emscripten.fd_t;
-pub const gid_t = emscripten.gid_t;
-pub const ifreq = emscripten.ifreq;
-pub const ino_t = emscripten.ino_t;
-pub const mcontext_t = emscripten.mcontext_t;
-pub const mode_t = emscripten.mode_t;
-pub const msghdr = emscripten.msghdr;
-pub const msghdr_const = emscripten.msghdr_const;
-pub const nfds_t = emscripten.nfds_t;
-pub const nlink_t = emscripten.nlink_t;
-pub const off_t = emscripten.off_t;
-pub const pid_t = emscripten.pid_t;
-pub const pollfd = emscripten.pollfd;
-pub const rlim_t = emscripten.rlim_t;
-pub const rlimit = emscripten.rlimit;
-pub const rlimit_resource = emscripten.rlimit_resource;
-pub const rusage = emscripten.rusage;
-pub const siginfo_t = emscripten.siginfo_t;
-pub const sigset_t = emscripten.sigset_t;
-pub const sockaddr = emscripten.sockaddr;
-pub const socklen_t = emscripten.socklen_t;
-pub const stack_t = emscripten.stack_t;
-pub const time_t = emscripten.time_t;
-pub const timespec = emscripten.timespec;
-pub const timeval = emscripten.timeval;
-pub const timezone = emscripten.timezone;
-pub const ucontext_t = emscripten.ucontext_t;
-pub const uid_t = emscripten.uid_t;
-pub const utsname = emscripten.utsname;
-
-pub const _errno = struct {
-    extern "c" fn __errno_location() *c_int;
-}.__errno_location;
-
-pub const Stat = emscripten.Stat;
-
-pub const AI = struct {
-    pub const PASSIVE = 0x01;
-    pub const CANONNAME = 0x02;
-    pub const NUMERICHOST = 0x04;
-    pub const V4MAPPED = 0x08;
-    pub const ALL = 0x10;
-    pub const ADDRCONFIG = 0x20;
-    pub const NUMERICSERV = 0x400;
-};
-
-pub const NI = struct {
-    pub const NUMERICHOST = 0x01;
-    pub const NUMERICSERV = 0x02;
-    pub const NOFQDN = 0x04;
-    pub const NAMEREQD = 0x08;
-    pub const DGRAM = 0x10;
-    pub const NUMERICSCOPE = 0x100;
-    pub const MAXHOST = 255;
-    pub const MAXSERV = 32;
-};
-
-pub const EAI = enum(c_int) {
-    BADFLAGS = -1,
-    NONAME = -2,
-    AGAIN = -3,
-    FAIL = -4,
-    FAMILY = -6,
-    SOCKTYPE = -7,
-    SERVICE = -8,
-    MEMORY = -10,
-    SYSTEM = -11,
-    OVERFLOW = -12,
-
-    NODATA = -5,
-    ADDRFAMILY = -9,
-    INPROGRESS = -100,
-    CANCELED = -101,
-    NOTCANCELED = -102,
-    ALLDONE = -103,
-    INTR = -104,
-    IDN_ENCODE = -105,
-
-    _,
-};
-
-pub const fopen64 = std.c.fopen;
-pub const fstat64 = std.c.fstat;
-pub const fstatat64 = std.c.fstatat;
-pub const ftruncate64 = std.c.ftruncate;
-pub const getrlimit64 = std.c.getrlimit;
-pub const lseek64 = std.c.lseek;
-pub const mmap64 = std.c.mmap;
-pub const open64 = std.c.open;
-pub const openat64 = std.c.openat;
-pub const pread64 = std.c.pread;
-pub const preadv64 = std.c.preadv;
-pub const pwrite64 = std.c.pwrite;
-pub const pwritev64 = std.c.pwritev;
-pub const setrlimit64 = std.c.setrlimit;
-
-pub extern "c" fn sigaltstack(ss: ?*stack_t, old_ss: ?*stack_t) c_int;
-pub extern "c" fn pipe2(fds: *[2]fd_t, flags: std.c.O) c_int;
-pub extern "c" fn getentropy(buffer: [*]u8, size: usize) c_int;
-
-pub const pthread_attr_t = extern struct {
-    __size: [56]u8,
-    __align: c_long,
-};
-
-pub const pthread_key_t = c_uint;
-pub const sem_t = extern struct {
-    __size: [__SIZEOF_SEM_T]u8 align(@alignOf(usize)),
-};
-
-const __SIZEOF_SEM_T = 4 * @sizeOf(usize);
-
-pub const RTLD = struct {
-    pub const LAZY = 1;
-    pub const NOW = 2;
-    pub const NOLOAD = 4;
-    pub const NODELETE = 4096;
-    pub const GLOBAL = 256;
-    pub const LOCAL = 0;
-};
-
-pub const dirent = extern struct {
-    ino: c_uint,
-    off: c_uint,
-    reclen: c_ushort,
-    type: u8,
-    name: [256]u8,
-};