Try harder to select quoted objects

Select string objects properly with `vi"`, `va"`, `vi'` and `va'`.

```
char *str = "viquote works here.";
char ch = '"';
char *str = "viquote doesn't work here.";
```

Ignore escaped quotes.

Only current line should be taken into account.

If text cursor is in front of all text object it should select the following one.