try / finally blocks are allowed but do nothing

[Caephler]

try / finally blocks should not be allowed but they are in Source. (tried in both S1 and S2)
Sample code:

try {
    display("1");
} finally {
    display("2");
}

Both display calls do not run, but the interpreter does not throw an error. Including a catch block will still result in an error, which is working as intended.

[thomastanck]

Closing in favour of #129, a combination of a bunch of issues, to clean up the list of issues a little.