Expand Qnone and Qnull macros

In the past, `Qnone` and `Qnull` had different values
in ripper context like below.
However 89cfc15 removes the usage in ripper context,
then expand the macro.

```
#ifndef RIPPER
# define Qnone 0
# define Qnull 0
#else
# define Qnone Qnil
# define Qnull Qundef
#endif
```

Author: yui-knk