Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/errno.pyi

@@ -0,0 +1,137 @@
+from typing import Mapping
+
+errorcode: Mapping[int, str]
+
+EPERM: int
+ENOENT: int
+ESRCH: int
+EINTR: int
+EIO: int
+ENXIO: int
+E2BIG: int
+ENOEXEC: int
+EBADF: int
+ECHILD: int
+EAGAIN: int
+ENOMEM: int
+EACCES: int
+EFAULT: int
+ENOTBLK: int
+EBUSY: int
+EEXIST: int
+EXDEV: int
+ENODEV: int
+ENOTDIR: int
+EISDIR: int
+EINVAL: int
+ENFILE: int
+EMFILE: int
+ENOTTY: int
+ETXTBSY: int
+EFBIG: int
+ENOSPC: int
+ESPIPE: int
+EROFS: int
+EMLINK: int
+EPIPE: int
+EDOM: int
+ERANGE: int
+EDEADLCK: int
+ENAMETOOLONG: int
+ENOLCK: int
+ENOSYS: int
+ENOTEMPTY: int
+ELOOP: int
+EWOULDBLOCK: int
+ENOMSG: int
+EIDRM: int
+ECHRNG: int
+EL2NSYNC: int
+EL3HLT: int
+EL3RST: int
+ELNRNG: int
+EUNATCH: int
+ENOCSI: int
+EL2HLT: int
+EBADE: int
+EBADR: int
+EXFULL: int
+ENOANO: int
+EBADRQC: int
+EBADSLT: int
+EDEADLOCK: int
+EBFONT: int
+ENOSTR: int
+ENODATA: int
+ETIME: int
+ENOSR: int
+ENONET: int
+ENOPKG: int
+EREMOTE: int
+ENOLINK: int
+EADV: int
+ESRMNT: int
+ECOMM: int
+EPROTO: int
+EMULTIHOP: int
+EDOTDOT: int
+EBADMSG: int
+EOVERFLOW: int
+ENOTUNIQ: int
+EBADFD: int
+EREMCHG: int
+ELIBACC: int
+ELIBBAD: int
+ELIBSCN: int
+ELIBMAX: int
+ELIBEXEC: int
+EILSEQ: int
+ERESTART: int
+ESTRPIPE: int
+EUSERS: int
+ENOTSOCK: int
+EDESTADDRREQ: int
+EMSGSIZE: int
+EPROTOTYPE: int
+ENOPROTOOPT: int
+EPROTONOSUPPORT: int
+ESOCKTNOSUPPORT: int
+ENOTSUP: int
+EOPNOTSUPP: int
+EPFNOSUPPORT: int
+EAFNOSUPPORT: int
+EADDRINUSE: int
+EADDRNOTAVAIL: int
+ENETDOWN: int
+ENETUNREACH: int
+ENETRESET: int
+ECONNABORTED: int
+ECONNRESET: int
+ENOBUFS: int
+EISCONN: int
+ENOTCONN: int
+ESHUTDOWN: int
+ETOOMANYREFS: int
+ETIMEDOUT: int
+ECONNREFUSED: int
+EHOSTDOWN: int
+EHOSTUNREACH: int
+EALREADY: int
+EINPROGRESS: int
+ESTALE: int
+EUCLEAN: int
+ENOTNAM: int
+ENAVAIL: int
+EISNAM: int
+EREMOTEIO: int
+EDQUOT: int
+ECANCELED: int  # undocumented
+EKEYEXPIRED: int  # undocumented
+EKEYREJECTED: int  # undocumented
+EKEYREVOKED: int  # undocumented
+EMEDIUMTYPE: int  # undocumented
+ENOKEY: int  # undocumented
+ENOMEDIUM: int  # undocumented
+ENOTRECOVERABLE: int  # undocumented
+EOWNERDEAD: int  # undocumented
+ERFKILL: int  # undocumented