Media Queries operators fail

Hello,

When some operators (such as `,` or `and`) are mixed in a media query, the parser doesn't guess when 2 MQ are the same.

For exemple : 

```
@media print, screen {a {color: #f00}}
@media screen, print {a {color: #f00;}}
```

Should output : 

```
@media print,screen{a{color:red}}
```

But the result is : 

```
@media print,screen{a{color:red}}@media screen,print{a{color:red}}
```
