Restore usage of _fseeki64 and _ftelli64 on Windows (#2185)

These overrides were removed in b732f59472,
but that broke handling of >2GiB files for `seekSize`.

include/platform.hpp

@@ -67,6 +67,13 @@
 	#define setmode(fd, mode) (0)
 #endif
 
+// Windows has 32-bit `long`, which limits `fseek` and `ftell` to 2 GiB
+#if defined(_MSC_VER) || defined(__MINGW32__)
+	#include <stdio.h> // IWYU pragma: export
+	#define fseek _fseeki64
+	#define ftell _ftelli64
+#endif
+
 // Apple has deprecated `sprintf` since Xcode 14 (for macOS 13), but we use it solely in
 // contexts where both the size of the buffer *and* max size of the printed string are
 // known statically, which GCC thus checks for.