defining uintptr_t = usize and intptr_t/ptrdiff_t = isize, and using uintptr_t to define size_t, and intptr_t to define ssize_t.

2. implement Debug for big size array
3. remove code related to epoll
4. use 'pub enum' for _Vx_semaphore

This value can vary at runtime.  Applications should instead use
sysconf(3) with _SC_AIO_LISTIO_MAX.

This constant is not stable across OS versions, so it cannot be used in
any backwards- or forwards- compatible way.  It's typically used to size
arrays in the kernel and in debugging utilities that are closely tied to
the OS version.  Since libc is ignorant about OS versions, we shouldn't
even be defining it.

This adds `utmpname(3)` on Linux with GNU libc.

Ref: https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/baselib-utmpname-3.html

This adds a few missing constants from DragonflyBSD `utmpx.h`.

Ref: http://gitweb.dragonflybsd.org/dragonfly.git/blob/HEAD:/include/utmpx.h

This adds a few missing constants from FreeBSD `utmpx.h`.

Ref: https://github.com/freebsd/freebsd/blob/a1d2b5187332a366a897689c5fb41d38d7e1b0d8/include/utmpx.h

This reverts commit 9df2deb3.

Adding OpenBSD as per request, verified here: https://github.com/openbsd/src/blob/master/sys/sys/stat.h#L188

These changes bring the types up to parity with recent Emscripten
versions using the upstream LLVM wasm backend. These changes should be
coordinated with the upgrade of rustc's Emscripten support. See
https://internals.rust-lang.org/t/upgrading-rust-s-emscripten-support/10684