Improved errors for 'catch'/'finally' blocks missing 'try' statements

### `try`-less `catch` Blocks
If the parser now sees

```TypeScript
catch (x) {
}
```
or
```TypeScript
catch (x) {
}
finally {
}
```
the user will be issued the message

> ~~A 'catch' clause must be preceded by a 'try' statement.~~

> 'try' expected.

_________________

### `try`-less `finally` Blocks
If the parser now sees

```TypeScript
finally { }
```

the user will be issued the message

> ~~A 'finally' block must be preceded by a 'try' statement.~~

> 'try' expected.

____________

Fixes #216.