Fix compiler warning

src/winscard_msg.c:249:17: warning: implicit conversion loses integer precision: 'ssize_t' (aka 'long') to 'int' [-Wshorten-64-to-32]
                        bytes_read = read(filedes, buffer, remaining);
                                   ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

src/winscard_msg.c

@@ -238,7 +238,7 @@ INTERNAL LONG MessageReceiveTimeout(uint32_t command, void *buffer_void,
  /* try to read only when socket is readable */
  if (pollret > 0)
  {
- int bytes_read;
+ ssize_t bytes_read;
 
  if (!(read_fd.revents & POLLIN))
  {