Allow trailing semi-colons

[skx]

This is fine:

let key="Name"
let val="Steve"

But if you add a trailing semi-colon, which habit forces upon me you get an error:

$ cat temp.in
let key="Name"
let val="Steve";
$ ./marionette temp.in
Error:expected '{', got {EOF }

Ideally we'd allow the trailing semi-colon, but if we don't we could have a better error message.