Fixing typeof undefined optimization

Commit mishoo/UglifyJS2@aebafad41eab48f43ed649ce8c77e8f1528b50da for #143 broke the typeof undefined optimization and failed test cases for #105:

```javascript
// This line
a = typeof b.c != "undefined"

// Used to be compressed into the following line WITH the unsafe option
a=b.c!==void 0

// Now it became
a=typeof b.c!="undefined";
```

These commits fixed the addressed issue, made changes to test case #105 to accommodate the modified sort behavior, and added test cases for #143.