missing "ghost" keywords when printing expressions in methods

[danmatichuk]

In this example:
`method M() {
ghost var h := var ta := F(); 5;
var j := ghost var tb := F(); 5;
assert h == j;
}

function F(): int { 5 }
`
The printer omits both "ghost" keywords, which throws an error when re-parsing.
Added relevant test in 021226d