Unused variables

[Martin Stjernholm, Roxen IS @ Pike developers forum]

The unused variables warning really finds a lot in Roxen. However, it
misses cases with initial assignments, e.g:

  void main()
  {
    int foo = 453;
    return 0;
  }

Would it be possible to extend it to catch these too?

Ideally it should only count non-lvalue references so e.g. even this
one would count as an unused variable:

  void main()
  {
    string foo;
    write ("hello world\n");
    foo = Stdio.stdin->gets();
    return 0;
  }