Fix broken Windows buiilds after own recent commit in read/write code.

Usual issue of win32 not following POSIX standards.

source/blender/blenloader/intern/readfile.h

@@ -24,6 +24,10 @@
 
 #pragma once
 
+#ifdef WIN32
+#  include "BLI_winstuff.h"
+#endif
+
 #include "DNA_sdna_types.h"
 #include "DNA_space_types.h"
 #include "DNA_windowmanager_types.h" /* for ReportType */

source/blender/blenloader/intern/undofile.c

@@ -252,7 +252,11 @@ bool BLO_memfile_write_file(struct MemFile *memfile, const char *filename)
   }
 
   for (chunk = memfile->chunks.first; chunk; chunk = chunk->next) {
+#ifdef _WIN32
+    if ((size_t)write(file, chunk->buf, (uint)chunk->size) != chunk->size) {
+#else
     if ((size_t)write(file, chunk->buf, chunk->size) != chunk->size) {
+#endif
       break;
     }
   }