moved the lseek() and stat() magic defines to setup.h and now take advantage

of struct_stat in formdata.c as well, to support formpost uploads of large
files on Windows too

lib/formdata.c

@@ -835,7 +835,7 @@ static CURLcode AddFormData(struct FormData **formp,
       /* Since this is a file to be uploaded here, add the size of the actual
          file */
       if(!strequal("-", newform->line)) {
-        struct stat file;
+        struct_stat file;
         if(!stat(newform->line, &file)) {
           *size += file.st_size;
         }