ios: Use _chsize_s on Windows for file truncation (JuliaLang#24616)

Should allow files >2 GB to be truncated on Windows.

Fix JuliaLang#24466

Checking Windows 32bit build https://julialang-s3.julialang.org/bin/winnt/x86/0.6/julia-0.6.1-win32.exe, libgit2.dll already uses `_chsize_s`, so both 32bit and 64bit should be able to use `_chsize_s`.

src/support/ios.c

@@ -566,7 +566,7 @@ int ios_trunc(ios_t *s, size_t size)
 #if !defined(_OS_WINDOWS_)
         if (ftruncate(s->fd, size) == 0)
 #else
-        if (_chsize(s->fd, size) == 0)
+        if (_chsize_s(s->fd, size) == 0)
 #endif
             return 0;
     }