Make improvements

- Introduce ualarm() function
- Make rename() report EISEMPTY on Windows
- Always raise EINVAL upon open(O_RDONLY|O_TRUNC)
- Add macro so ./configure will detect SOCK_CLOEXEC
- Fix O_TRUNC without O_CREAT not working on Windows
- Let fcntl(F_SETFL) change O_APPEND status on Windows
- Make sure pwrite() / pread() report ESPIPE on sockets
- Raise ESPIPE on Windows when pwrite() is used on pipe
- Properly compute O_APPEND CreateFile() flags on Windows
- Don't require O_DIRECTORY to open directories on Windows
- Fix more instances of Windows reporting EISDIR and ENOTDIR
- Normalize EFTYPE and EMLINK to ELOOP on NetBSD and FreeBSD
- Make unlink() / rmdir() work on read-only files on Windows
- Validate UTF-8 on Windows paths to fix bug with overlong NUL
- Always print signal name to stderr when crashing due to SIG_DFL
- Fix Windows bug where denormalized paths >260 chars didn't work
- Block signals on BSDs when thread exits before trashing its own stack

third_party/lua/luaencodeluadata.c

@@ -192,7 +192,7 @@ static int SerializeString(lua_State *L, char **buf, int idx) {
   size_t i, n;
   const char *s;
   s = lua_tolstring(L, idx, &n);
-  utf8 = _isutf8(s, n);
+  utf8 = isutf8(s, n);
   RETURN_ON_ERROR(appendw(buf, '"'));
   for (i = 0; i < n; i++) {
     switch ((x = kLuaStrXlat[(c = s[i] & 255)])) {