Add detection of usage of unbound variables

[Martin Sjölund]

We need to add detection of usage of unbound variables

protected
  Real r;
algorithm
  x := f(r); // Detect me and show a warning

The major design decision here is to choose to detect variables that may be unbound or only those that must be unbound (how to merge branches).

[Martin Sjölund]

How the hell do you CC Jens you stupid little trac D:

[Martin Sjölund]

Fixed in r12733. We now print a warning saying this is bad.