message: fix compile error for cpp_moulde
diff: @@ -359,7 +359,7 @@ static sw_inline int mysql_decode_field(char *buf, int len, mysql_field *col)
  /**
  * string buffer
  */
  - char *_buffer = emalloc(len);
  + char *_buffer = (char*)emalloc(len);
  if (!_buffer)
  {
  return -SW_MYSQL_ERR_BAD_LCB;
  