formdata: check for EOF when reading from stdin

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.

 * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.

 *

 * This software is licensed as described in the file COPYING, which

 * you should have received as part of this distribution. The terms

            char buffer[512];

            while((nread = fread(buffer, 1, sizeof(buffer), fileread)) != 0) {

              result = AddFormData(&form, FORM_CONTENT, buffer, nread, &size);

              if(result)

              if(result || feof(fileread) || ferror(fileread))

                break;

            }

          }